Most of the primer vehicles I have seen, have a acouple coats of clear over the top to avoid the moisture retention and oxidation you are speaking of.
If I am reading you right, you want a little shine, I would look into a single stage like lacquer. You can buff and wet sand to your desired degree of shine. It is also easy to spray without a booth 'cause you are going to buff it out anyway, dirt and impurities are not a big issue. It is very durable as well. My .02.
Hank
