24 Once the DP40 has dried, we can begin wet-sanding the primer/sealer in anticipation of our upcoming topcoat. Using 400-grit paper and a rubber sanding block, the complete body is sanded. Watch out for sharp corners so that you don't break through the primer coat. Wash the panel down and look for any traces of the black guide paint. If you see any, the panel will need additional sanding or filler.