Coverage beats frantic movement
Fast random motions can cross the same center area repeatedly while leaving thin lines untouched. A deliberate pass pattern gives every part of the surface a turn. If the object does not finish, change one variable—angle, orientation, or edge focus—rather than repeating the identical sweep.
Rotation solves access, not progress by itself
The official PC control lists R for washer rotation. Use it when the tool shape blocks a clean pass or when an edge stays hidden. You still need to move the washer over the dirty pixels; rotation is a setup action, not an automatic clean command.
Diagnose the last dirty patch
When progress stalls, slow down and compare clean and dirty color along the object's perimeter. Check corners, narrow sides, undersides, handles, and the border between faces. Move the camera and your character because a missed patch can sit behind the current view even when the main face looks finished.