Answer
For primer overspray, use 600 lightly. Use 400 first only on heavier texture before repainting.
Why it happens
Dry primer dust can sit on the surface and needs light sanding without cutting into the surrounding finish.
Recommended grit
Use 600 for light primer overspray on prepared surfaces. Use 400 first only for heavier texture before repainting.
Wet or dry
Dry.
Success check
The surface feels smooth and is ready for the next coating step.
What to do
- Let primer overspray dry fully.
- Sand lightly with 600.
- Use 400 first only on heavier texture before repainting.
- Clean dust before applying paint.
Avoid: Do not sand through surrounding finish while removing overspray.