I use disposable cups on my clear coat only spray gun. After I finish, I'll leave whatever is left in the cup undisturbed. It can take a full month for the liquid to shrink to its final solid size. Even after a week it has only shrunk a third of its final size. This depends on weather conditions of course. The process can be speeded up or slowed down depending on the ratios of activator and reducer involved. I don't want a fast drying clear or I am more likly to get the dreaded overspray (a dulling) or orange peal (where the paint doesn't flow out smooth because it is hardening up too fast).