you can find high temp clearcoat at auto stores that dries a little harder, use 2 very very thin coats, wait twice as long as the can says to dry, put it in a warm, dry, place to dry.
also if your paint right now is a little bumpy, like most spray jobs, use a piece of dry paper towel and lightly wipe everything, it takes down the imperfections a little bit and makes the clear look better. dont get too carried away though, then there will be nothing for the clear to adhere to.
thats really the best you can do w/ a rattle can, expect lots of easy chips. looks good so far!