I been doing the same thing, for about a year.
But on Ace's, Dupli-color, plasti-kote, and other enamels.
Best Caps: NY Fat, NY Thins, Rusto stocks
As for the tiny leaks, cut down the male cap stem to where the v-slit ends.
Use a 1/8" screwdriver and hollow out the fan tip.
It should fit any cap afterwards.