Using grits higher than 800-1000, depending on whether you are speaking of CAMI or FEPA grade, decreases mechanical adhesion for topcoats and is not recommended. I shoot flowcoats over P800 and clear lays down nicely. Single stage(SS) metallics and painters with limited experience are not a good combination. These cars were not clearcoated, they were reflowed to achieve a unifom appearance. Start buffing SS and distrupt the metallic and blotchiness is the result. Today's lacquer is not formulated like that of 43 years ago. Urethanes are superior systems. Want more paint info on lacquer and urethane from professionals in collision and restoration? Go to Refinish Network: http://www.refinishnetwork.com/
People there paint all day, every day. I stopped using lacquer in 1984 shortly after entering the industry.