Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
My guess, and you've probably already realized this but whenever we print a grey base it flashes in at least half the time that white does. Anytime we slightly over flash a grey base we run into a not so smooth sand paper texture to the print. Like I said you've probably dialed the flash in with that ink but just a suggestion. Our grey base we use flashes in under 1 second which is quite a bit faster then our white.
Got a heat press?......teflon sheet + heat press....will fix it in a pinch.