Short answer. yes. You can base over #600 or finer. I wouldn't go any finer than#800. Spot seal any bare steal or filler with a DTM sealer.
Would I? No. Not on a complete refinish. The main reason for me is if something is going to go wrong, IE. fisheyes or what have you, I want it to go wrong in the sealer coat and not in my color coat.
