150 or 180 for a rough sand, say I'm just sanding off the small ridges and bumps in between layers. Or the place is going to be sprayed with knock down or orange peel. (Level 3)
220 for fine sanding.
I'll usually sand 2 or 3 passes 220 using an electric sander then use 220 grid sanding piles to get rid of any swirl marks then do over it with lights and a sanding spong and used 220 grit sanding paper.
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