Guide content
The grit scale, simplified
Sandpaper grit numbers are inverse-proportional to grain size — lower numbers are coarser, higher numbers are finer. The most important thing to know: skipping more than 100 grit steps in a progression leaves scratches the finer paper can't level out.
The pro progression for a respray
| Stage | Grit | Use |
|---|---|---|
| Body filler shaping | 36–40 | Aggressive cut on fresh filler. Use a hand block or DA with a 6" pad. |
| Filler feathering | 80–120 | Feather the filler edge into surrounding metal/primer. DA-only. |
| Primer prep | 180–220 | Final cut before 2K primer. Eliminates the 80-grit scratches. |
| Primer block-sand | 320 (dry) or 400 (wet) | Level the primer film smooth. Reveals low spots. |
| Final pre-basecoat | 500–600 (wet) | Smoothest finish before color. Some shops go to 600 dry instead. |
| Clearcoat cut (if reflow needed) | 1000–1500 (wet) | Remove orange peel before polish. |
| Clearcoat polish prep | 2000–3000 (wet) | Finest scratches before buffing compound. |
Wet vs dry sanding
Dry sanding is faster, doesn't introduce moisture into the panel, and works for primer cut, body filler shaping, and feathering. Most shops dry-sand through 320, then wet-sand 400+.
Wet sanding uses water (sometimes with a few drops of dish soap) as a lubricant. It eliminates clogging, produces a finer finish, and cools the panel. Required for cutting clear coat.
Backing pad sizes matter
- 6" pads — standard for DA sanders. Most common.
- 5" pads — better for tight curves and edges.
- 3" mini pads — for spot repair, jambs, and tight areas.
- Long boards (longboards) — 16"–30" hand boards for large flat panels (hoods, doors). Critical for show-quality finish.
Hook-and-loop vs PSA
Hook-and-loop (Velcro) backed paper attaches and removes from a matching pad. Fast to swap. Wears out the pad over time but is the production standard. Eagle Abrasives MaxFilm, 3M Hookit, Norton hook-loop.
PSA (pressure-sensitive adhesive) paper sticks once, then peels off. Cleaner cut on long boards. 3M Stikit, Norton A275 PSA.
Most shops run hook-and-loop on DAs and PSA on long boards.
Disc styles by job
Solid sanding discs
Standard hook-and-loop discs with no holes. Best for filler shaping and rough cutting. Tend to load up faster without dust extraction.
Multi-hole "Hookit Clean Sanding" discs
Discs with many small holes that mate to a vacuum-equipped DA. Drastically reduce dust, extend disc life, and produce a cleaner sand scratch. 3M Cubitron II 737U is the gold standard.
Film-backed discs
Polyester film instead of paper backing. Resists tearing, sands flatter for primer/clear stages. Eagle MaxFilm, Norton Premium 1.
Brand recommendations by stage
Filler shaping (36–120)
3M Cubitron II 36+ for fastest cut. 3M 977F P80 hand-feathering rolls for blending edges.
Primer prep (180–320)
Eagle Abrasives MaxFilm 220 hook-and-loop. 3M Hookit 320 multi-hole for vacuum DA setups.
Pre-basecoat finish (500–600)
3M Hookit 500 wet/dry. Norton A275 No-Fil 600 for fewer scratches.
Clearcoat reflow (1000–3000)
3M Trizact 3000 for the final cut before polish. Norton ICE 2000/3000 also excellent.
Common mistakes
- Going too fine too early — 800 grit can't remove 80-grit scratches efficiently. Step up gradually.
- Wet-sanding primer — soaks moisture into the film. Wait until 400+ grit for water-based sanding.
- Sanding without dust extraction — loads up paper, reduces life 3x, and leaves abrasive dust under the next coat.
- Using a worn pad with new paper — uneven cut. Replace pads every 50–100 hours of use.
Our recommendations
Below are the abrasives we re-stock weekly. Each step is represented by the brand and grit pros prefer for that stage.
