Just primer and sand smooth. I only use automotive finishes. The whole point of primer is to build up thick so you can sand it back down smooth to make a real nice surface to paint on. Unfortunately nothing good comes from a rattle can. You need to use real professional products. A good automotive primer is catalyzed so when you paint on it, it wont absorb the solvents from the paint and shrink back into the layer marks that our printers make. Once its smoothed and the base color is on then you apply a good urethane clearcoat. After its cured you can take it a step further if you want and sand and buff the finish