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What Grit Sandpaper for Body Filler, Primer and Paint? An Australian Workshop Guide
Featured image idea: A real Australian panel shop prep bay. One tech is block sanding filler on a quarter panel, another DA-sanding primer with a vacuum-connected multi-hole disc. Bench in the background with clearly labelled grits: P80, P150, P180, P320, P600. No fake glossy showroom look. Keep it dusty, organised, and believable.
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Intro
If the finish keeps coming back with scratches, sink-back, pigtails, or edges showing through, the problem usually starts way earlier than the spray gun. It starts in prep. Wrong grit, skipped steps, a clogged disc, too much pressure, no guide coat, no extraction. Same old story.
This guide is built for Australian panel shops, spray painters, workshop owners, and tradies who want a grit sequence that works in the real world. Not theory. Not fluff. Just what to use, when to use it, where people stuff it up, and how to get through jobs faster without buying rework. The grit ranges and workflow notes below line up with current Australian collision-repair guidance, Australian supplier guidance, and local sanding product specs.
Key takeaways
| What matters | Practical answer |
|---|---|
| Best starting grit for body filler | Usually P80 |
| Next step after P80 | Usually P120–P180 |
| Final filler prep before primer | Usually P240–P320, then P400–P600 if your system calls for it |
| Primer sanding before colour | Commonly P400–P600, sometimes finer depending on system and colour |
| Clear coat denib / correction | Commonly P1500–P2000+ wet |
| Biggest time-waster | Skipping grits and trying to “polish out” deep scratches later |
| Biggest finish killer | Worn discs, no guide coat, poor dust extraction, too much pressure |
The numbers above are consistent with current 3M Australia repair SOPs, an Australian body-filler grit guide published in 2026, and local primer-filler product guidance.
Why grit choice matters more than most workshops admit
A lot of bad paint jobs are really bad sanding jobs wearing paint on top. If you leave coarse scratches behind, they can print through later. If you go too fine too early, the surface can lose the mechanical key the next layer needs. 3M’s Australian collision-repair material keeps coming back to the same points: use the right grit for the stage, use guide coat to spot the misses, and keep dust under control so the finish stays consistent.
For workshops, grit choice is not just about finish. It is also about cycle time. Australian Paint & Panel notes that dry sanding can lift productivity, clean up the shop floor, and improve the overall finish, but only if extraction is sorted properly. That is the bit plenty of shops half-do and then wonder why discs load up and jobs bog down.
Pro Tip: If a disc is loading, smearing, or starting to leave random marks, stop being stingy and change it. Burning ten extra minutes to save one disc is false economy.
Image placeholder: Close-up of a sanded primer surface under low-angle light, showing one half with clean uniform scratch pattern and the other half with deep leftover scratches and pigtails.
The grit sequence that works
The table below pulls together Australian collision-repair SOPs, local supplier guidance, and current local product recommendations. Treat it as a practical workshop baseline, then confirm against the TDS for the filler, primer, and topcoat system you are actually spraying.
| Stage | Typical grit | What you’re doing | Notes |
|---|---|---|---|
| Initial repair prep / strip area | P80 | Remove paint around repair and get to work area | DA is common here |
| Shape body filler | P80 | Knock down highs and establish shape | Use a block where you need flatness |
| Refine filler | P120–P150 | Remove P80 scratches and tighten shape | Don’t move on while P80 scratches are still there |
| Feather edge / refine repair | P180 | Blend repair edge and prep for glaze/primer | Common 3M step |
| Final filler surfacing | P240–P320 | Smooth and straighten | Good point to re-check with guide coat |
| Final prep before primer | P400–P600 | Leave suitable surface for primer | Depends on product system |
| Primer sanding before colour | P400–P600, sometimes P800 | Smooth primer for topcoat | Check the product sheet |
| Denib / clear correction | P1500–P2000+ wet | Remove nibs, texture, or clear imperfections | Follow with compound and polish |
1) Initial prep and stripping
For small damage repair, 3M Australia’s SOP starts with a grade 80 abrasive disc on a DA to remove paint in the repair area and extend the prep zone past the damage. That is a good, no-nonsense baseline for real workshop work.
2) Shaping body filler
Once the filler is cured, P80 is still the normal place to start. That is where you knock down bulk and get the panel back into shape. Eastern Auto Paints’ 2026 guide lines up with the same advice and makes the point clearly: coarse enough to cut, not so rough that you create extra drama for yourself later.
Pro Tip: On flatter panels, reach for a proper block, not just your hand. Hand-sanding filler without a block is how a “straight” panel turns into a wavy one.
3) Refining filler and feather edging
This is where jobs go wrong. After P80, the next job is not “make it smooth.” The next job is remove every P80 scratch. That usually means P120–P150, then P180 for feathering and refinement. 3M’s Australian SOPs repeatedly step through 80 → 150 → 180, with dry guide coat used between stages to show pinholes, scratches, highs, and lows.
4) Final prep before primer
From there, local guidance moves into P240–P320 and then P400–P600 when you are leaving the final surface for primer. Eastern Auto Paints sets out that progression clearly, and a local primer-filler listing also recommends a 400–600 final grit after drying for a smooth finish.
5) Sanding primer before colour
For many primer and surfacer systems, P400–P600 is the usual conversation. Some systems and colours will push you finer. If you are spraying something unforgiving, especially metallics or a dark finish that shows every sin, this is not the stage to get lazy.
6) Wet sanding for denibbing and clear-coat correction
Once you are in defect removal, denibbing, orange peel work, or clear-coat correction, you are usually into P1500–P2000 and beyond. Local automotive suppliers and repair packs commonly stock that range for wet sanding work.
Image placeholder: Bench layout of actual abrasive stages in order: P80 disc, P150 strip, P180 disc, P320 disc, P600 wet-and-dry sheets, P1500/P2000 finishing sheets. Use a workshop bench, not a studio tabletop.
Which abrasive type makes sense
Grit is only half the call. The other half is the abrasive itself. Paper, film, net, aluminium oxide, ceramic, multi-hole layouts, backing type, dust handling. That is where a lot of shops either save time or chew through boxes.
The comparison below is built from 3M Australia, Mirka-related Australian supplier guidance, Bona Australia, PFERD Australia, and an Australian abrasives guide for fabrication.
| Abrasive / format | Best use | Strengths | Watch-outs |
|---|---|---|---|
| Aluminium oxide paper disc | General prep, everyday sanding | Fast cut, common, easy to source, good value | Can load faster than better film/net options |
| Ceramic or ceramic-blend disc | Heavier production work, hard surfaces, shops chasing speed and life | Longer life, fast continuous cut, good for high-throughput work | Higher buy price |
| Film-backed disc | Primer, filler, clear, cleaner finish work | Better tear resistance and edge wear | Costs more than basic paper |
| Net / strong multi-hole disc | Dry sanding with extraction | Better dust flow, less loading, cleaner work area | Only worth it if extraction is decent |
| Wet-and-dry silicon carbide sheet | Primer sanding, denibbing, clear correction | Flexible, fine finish, good wet | Not for heavy shaping |
| Rigid sanding block + strip/sheet | Filler shaping on flatter panels | Helps keep panels straight | Slower than DA for broad prep if used everywhere |
3M says its purple clean-sanding disc uses aluminium oxide with a stearate coating and a multi-hole pattern to resist loading, clear dust, and speed disc changes. Mirka-related Australian supplier guidance says its ceramic/aluminium-oxide mixes and film backings are built to reduce clogging and keep cutting longer. Bona Australia says ceramic abrasives are designed for long service life in demanding work.
Pro Tip: If your shop burns through a lot of P80, P150 and P180 every week, the cheapest disc is rarely the cheapest job. Faster cut, better dust handling, and longer disc life usually matter more than the ticket price on one box.
Image placeholder: Side-by-side photo of three 150 mm discs on a prep trolley: basic paper disc, film disc, and multi-hole/net-style disc, with visible dust extraction hose nearby.
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Common mistakes that cost time and finish quality
1) Skipping grits
Jumping from P80 straight to P400 is not a shortcut. It is how you hide deep scratches until primer or colour makes them obvious. Local Australian guidance on filler sanding calls this out directly.
2) Sanding without guide coat
Dry guide coat exists for a reason. 3M Australia says it reveals pinholes, scratches, ripples, and missed body lines, and it can be used in wet or dry sanding. If you are sanding filler or primer blind, you are guessing.
3) Running worn discs too long
3M warns that worn or clogged abrasives can contribute to pigtails and inconsistent scratch patterns. Australian Mirka reseller guidance says the same thing in plain language: worn discs, cheap paper, wrong grit, bad speed, too much force, and bad dust extraction all lead to ugly scratch marks.
4) Leaning on the sander
Too much pressure does not make the job faster. It makes heat, loads the abrasive, and increases the risk of random marks. The Australian pigtail guidance specifically calls out excessive force and poor sander settings.
5) Treating extraction like an optional extra
Paint & Panel Australia makes the trade-off pretty clear: dry sanding can be cleaner and faster, but only if dust extraction is there to do the job. 3M’s Australian pages also tie dust control directly to finish consistency and disc life.
| Mistake | What it causes | Better move |
|---|---|---|
| Skipping grit steps | Deep scratches showing later | Work through the full sequence |
| No guide coat | Missed lows, pinholes, body lines | Dust guide coat between stages |
| Running clogged discs | Pigtails, heat, wasted time | Change discs earlier |
| Too much pressure | Uneven scratch pattern | Let the abrasive cut |
| Poor extraction | Loading, dust in finish, shorter disc life | Use proper vacuum flow |
A faster workflow that still leaves a clean finish
This is where good shops separate themselves from messy ones. Not by doing some secret trick. Just by being disciplined.
Standardise your core grits
For most automotive prep bays, your most-used stack is going to live around P80, P150, P180, P320, P600, with finer wet-and-dry on hand for finishing work. Australian suppliers stock these common grits heavily in disc and sheet form for a reason.
Block first, DA after where it makes sense
3M’s repair SOPs keep hand-blocking and DA work in the same process, not as an either/or fight. That makes sense in a real shop. Use the block to keep the panel honest. Use the DA where it saves labour without wrecking the shape.
Run dry where practical, but only with proper extraction
Dry sanding is faster and cleaner when the setup is right. If extraction is poor, you lose the benefit and create new problems.
Buy for throughput, not just shelf price
For workshops running volume, trade pricing on your main consumables can cut costs properly over time. That matters more than chasing the absolute cheapest mixed pack when you are burning through discs every week. The good play is to lock in the grits you use every day, then buy smarter around those.
Pro Tip: Keep one “do not run out” consumables shelf: P80, P150, P180, P320, P600, guide coat, masking, and a few proper blocks. Running out of the basics is how prep bays slow down.
| Workshop habit | Result | Better workshop habit |
|---|---|---|
| Mixed random grits in half-used boxes | Slower prep, more mistakes | Standard core grits and clear reorder points |
| Cheap discs for every job | Higher loading and more disc changes | Better discs on high-volume stages |
| No guide coat unless it’s a hard job | Missed defects | Guide coat as normal process |
| Dust extraction used inconsistently | Messy prep and random scratches | Extraction connected every time |
| One grit trying to do too much | Rework later | Use the right grit for the stage |
Image placeholder: Australian workshop consumables shelf with labelled bins: P80, P150, P180, P320, P600, guide coat, sanding blocks, wet-and-dry sheets, masking tape.
Quick notes for cabinet makers and fabricators
This article is panel-shop first, but the same basic rule still applies in wood and metal: do not skip the scratch-removal steps.
Australian woodworking guidance points to a simple progression where rough sanding often starts around 60–80, general smoothing around 120, and finishing around 180–240, with finer steps used when the finish system demands it. For fabrication, an Australian abrasives guide notes common metalworking ranges such as 24–40 for heavy grinding, 60 for weld removal, 80 for blending, and 120 for finishing, with the abrasive type changing depending on whether you need grinding discs, flap discs, belts, or fibre discs.
| Trade | Typical starting point | Common finishing point | Best note |
|---|---|---|---|
| Cabinet making / timber | P60–P80 | P180–P240, sometimes finer | Don’t jump grits on hardwood |
| Metal fabrication | P24–P60 for aggressive work | P80–P120 for blending/finish | Choose the right disc type, not just grit |
| Auto refinishing | P80 for repair prep/filler shaping | P400–P600 before primer/colour, then finer wet | Scratch control matters more than speed |
Recommended product types
Not brands shoved down your throat. Just the categories that genuinely help.
- 150 mm multi-hole sanding discs
Good for cleaner dry sanding, better dust flow, and longer usable disc life when paired with extraction. - Dry guide coat
One of the cheapest ways to catch misses before they become repaint work. - Rigid and semi-flex sanding blocks
Worth having both. Straight work and contoured work are not the same job. - Wet-and-dry silicon carbide sheets
Handy for primer smoothing, denibbing, and fine correction work. - Ceramic or ceramic-blend discs for high-throughput work
Better fit when your workshop is doing volume and wants longer life with a strong cut.
FAQ
What grit sandpaper should I use on body filler?
Start around P80 to shape the filler, then work through P120–P150, then P180, then into P240–P320 and P400–P600 as you move toward primer prep.
What grit should I finish primer with before paint?
A lot of systems live around P400–P600, though some jobs and product systems go finer. Follow the primer and topcoat sheet you are actually using. Local primer-filler guidance and Australian supplier content both point to that general range.
Can I wet sand 2K primer before basecoat?
Yes, depending on the product system. Local guidance around primer sanding and wet-and-dry prep supports wet sanding in the finer stages, but the safe move is always to check the product’s own instructions first.
Do multi-hole sanding discs really make a difference?
Yes, when paired with extraction. 3M and local Australian suppliers both say the hole patterns improve dust evacuation, reduce loading, and help extend disc life.
What causes pigtails when sanding?
Common causes include poor-quality or worn abrasives, wrong grit, bad sander speed, too much pressure, worn backing pads, and poor dust extraction.
Are ceramic discs worth it?
For occasional use, not always. For shops sanding day in, day out, they often make sense because they hold cut longer and resist wear better. That matters when labour time costs more than the disc.
What is the biggest sanding mistake in workshops?
Skipping steps. The job looks fine until primer, colour, or clear starts showing what you left behind.
Sources
- 3M Australia – Small damage repair SOP
- 3M Australia – Abrasive productivity
- Paint & Panel Australia
- Eastern Auto Paints – What grit sandpaper for body filler
- 3M Australia – Clean sanding disc product page
- 3M Australia – Dry guide coat
- Best Abrasives Australia – Avoid pigtails and imperfections when sanding
- Wholesale Paint – Sandpaper collection
- Wood Review Australia – Sandpaper specifics
- VGA Autopaints – Sand paper pack repair prime paint
- Best Abrasives Australia – Which Mirka abrasive should you use?
- Paintmobile – Primer filler guidance
- Bona Australia – Ceramic abrasives
Suggested internal links
- 150mm ceramic sanding discs: faster cut and longer life for workshop use
- Mixed high grit sanding disc pack: ideal for primer prep and finishing stages
- 150mm base plate: reliable backing for consistent sanding performance
- Understanding abrasive cut rates: how to sand faster without sacrificing finish
- Trade accounts: unlock workshop pricing and bulk consumable savings
Final word
If you want cleaner prep, fewer comebacks, and less time wasted in the bay, stop treating sandpaper like an afterthought. Get the grit sequence right. Use guide coat. Run extraction properly. Change discs before they are dead. Buy the consumables you use every day like a workshop owner, not like someone doing one job on a Saturday.
That is where the finish starts.
