Answer
Smooth with 180 and 220. Use 320 or 400 for finer prep before painting.
Why it happens
The surface was not refined enough after removal or leveling.
Recommended grit
Use 180 and 220 for general smoothing; use 320 or 400 for finer prep.
Wet or dry
Dry for most prep.
Success check
The surface feels even and is clean before paint.
What to do
- Sand rough areas with 180.
- Refine the whole surface with 220.
- Use 320 or 400 if the coating needs finer prep.
- Clean dust completely before paint.
Avoid: Do not paint over rough ridges or coarse scratches.