Answer
Switch to a finer between-coats grit. Use 400 for primer leveling, 600 for paint or finish coats, and 800 or finer when the surface is close to final appearance.
Why it happens
Between-coats sanding is meant to level small nibs, not remove heavy material, so coarse grit leaves scratches that the next coat may not hide.
Recommended grit
Use 400 for primer, 600 for paint or finish coats, and 800 or finer near the final coat.
Wet or dry
Use dry sanding for coatings that are not water-safe. Use wet sanding only after the coat is fully cured and compatible with water.
Success check
The surface feels smooth, has only a fine even scratch pattern, and the next coat can cover it cleanly.
What to do
- Check whether you are sanding primer, paint, clear coat, or another finish.
- Use 400 grit only for primer or heavier leveling.
- Use 600 grit for most paint or finish coats.
- Use 800 or finer when the coat is thin or near final appearance.
- Sand lightly until nibs are removed.
- Wipe or rinse residue according to the coating type.
- Apply the next coat only after the surface is clean.
Avoid: Do not use coarse removal grits between coats. They can leave scratches that stay visible under the next coat.