Never mind the flat/gloss paint question. I fiddled around with some 1000 grit sandpaper and was able to smooth the surface enough to make my paint masks stick properly.
I am into model making, so I use Tamiya. I'm currently building the refit Enterprise and am painting the lower hull. Here is a pic of the strong back area. Once again, I'm fairly novice, so if I did well enough to impress myself, I wanted to show it off.