Sand out imperfections using more aggressive sandpaper. If the resulting surface requires primer, the final scratch should be no coarser than 320 in wet-or-dry sandpaper. Areas to be sprayed with color should have a final scratch of no coarser than 600 wet-or-dry. Areas to be sprayed with clear only, as in blend areas, call for a final scratch of no coarser than 1000 wet-or-dry. For purposes of selecting sandpaper grits metallic, pearl and base coat colors are more apt to show sand scratches than solid and single stage colors. After primer has been applied, usually 2-3 coats, wait a minimum of 2 hours before sanding. The exact waiting time is a function of primer build up and temperature but there is no harm in waiting overnight.