RE: Sanding Primer Question
Just a comment. If you are going to use white, yellow or some other bright colors, prime with white primer. The colors will be much brighter. I primed the fuselage on one plane with grey primer and couldn't get the yellow paint to match the Ultracote on the wings. Went over the painted yellow (after sanding it a lot) and primed with white. Repainted with yellow. Perfect match!