By no means am I an expert on paint, but I have shot several vehicles with Acrylic Enamel. The answer to your question is that it really depends on what you want. Acrylic Enamel is fairly easy to shoot. If you want a glass like finish, of course color sanding and buffing will give the best results. I have found that with the correct temp reducer, you can get a beautiful finish that few would bother to buff. To further answer your question, I don't think many competent painters sand and buff due to and unacceptable result when shooting it. It's just their preference.