Answer
Visible scratches under paint usually need 320 or 400 correction, then 600 for finer topcoat prep.
Why it happens
The final prep grit was too coarse, scratches were not refined, or primer did not fill the sanding marks.
Recommended grit
Use 320 or 400 before primer or paint. Use 600 for finer topcoat prep.
Wet or dry
Dry for normal prep.
Success check
The surface is smooth and scratches are not visible before the next coat.
What to do
- Let the paint or primer cure before correcting.
- Sand the scratches with 320 or 400.
- Refine with 600 for finer topcoat prep.
- Clean dust before repainting.
Avoid: Do not repaint over visible coarse scratches.