I have an old Super Aeromaster fuselage covered in Koverall and have about four coats of Minnwax Polycrylic on it. What is the best way to sand this stuff for an absolutely smooth surface to paint. I did lightly sand between coats with dry 320 grit. But in certain light, there seems to be streaks in the side of the fuse that I am afraid will show after painting. Can this stuff be wet sanded or should I stick to dry paper and a couple more coats?