Answer
For cured polyurethane runs, level with 400 or 600, then blend with 800 or 1000.
Why it happens
Runs need to cure before sanding, then they must be leveled without cutting through surrounding finish.
Recommended grit
Use 400 or 600 to level small cured runs, then 800 or 1000 for finer blending.
Wet or dry
Dry unless the finish instructions allow wet sanding.
Success check
The run is level and the repair blends into the surrounding finish.
What to do
- Let the run cure fully.
- Level the raised run with 400 or 600.
- Blend with 800 or 1000 if the surface is visible.
- Clean dust before recoating or polishing.
Avoid: Do not sand soft polyurethane that still smears.