Answer
For an interior door before painting, clean it, scuff with 180 or 220, then use 320 for finer smoothing.
Why it happens
The door needs a clean, dull, even surface so primer or paint lays flat.
Recommended grit
Use 180 or 220 for scuff sanding, then 320 for finer smoothing if needed.
Wet or dry
Dry.
Success check
The door face is dull, smooth, and free of dust before painting.
What to do
- Clean the door surface.
- Sand old gloss with 180 or 220.
- Blend brush marks or rough spots.
- Remove dust before primer or paint.
Avoid: Do not use coarse grit across a smooth visible door face unless stripping damaged finish.