Sorry, guess I should have mentioned it was Rustoleum Professional, I just figured it was a given, considering the thread.

Well, I think I'll just try starting over with new batch at a different store, since my F-i-L thought the yahoos working at this particular Menards were pretty clueless when it came to mixing the Rustoleum. Of course that means there's been two wasted weekends of work applying the current 6 coats on the fender, but at least it's only a fender I have to re-strip.