Answer
Refine primer with 320 or 400, then 600. Do not paint over visible coarse scratches.
Why it happens
The primer scratches were too coarse or not fully refined before painting.
Recommended grit
Refine primer with 320 or 400, then use 600 for finer final prep.
Wet or dry
Dry for most primer prep; wet only when the coating instructions allow it.
Success check
Primer is smooth and evenly dull before paint.
What to do
- Let primer cure as directed.
- Sand with 320 or 400 to remove visible scratches.
- Use 600 for finer final primer prep.
- Clean all dust before painting.
Avoid: Do not paint over visible coarse primer scratches.