Coarse-grit paper or sanding screens will leave undesirable ... with joint compound and finally sanding these spots when they dry. Go back over the walls and ceiling with a light and a sander.

To get a good near-polished finish, you will now need to use wet and dry paper. Wet the paper with a little water to reduce friction. Start with a 280 grit, then move on to 600 grit, and finally ...