It seems to me that when looking at Rustoleum the can for the spray paint had wording that did not match the can for non-spray. As if there was a difference in the contents of the paint. It seems to me it was somethings having to do with an oil that was in one but not in the other.

Also, I found that if I shoot primer from a can onto fiberglass I have to wait about five days before sanding. If I tried to sand before that amount of time had elapsed there was a good chance the the sandpaper would load up very easily so I assumed the paint was not completely dry. After five days I could sand to my heart's content. So I made it a practice to prime then let the fuselage remain idle for five days before doing anything with it.