Re: Exercises away from the kit that work for you.
Anything choppy on your thighs or with your feet should work there. Try this:
R R R R R R R R LRLRLRLRLRLRLRLRL L L L L L L L RLRLRLRLRLRLRLRL
Or any exercise/variation you dig, really. In my experience, speed comes a lot more from developing relaxed, precise control than from doing huge amounts of endurance-focused practice. IE; once you can control the specific idea/related-technique effortlessly (more or less), endurance becomes much less of an issue. So keep your mind on relaxation, breathing, solid feel and clean rhythm, even with your fingers on your desk (trying doing that pattern with each R/L pair of fingers, ring fingers can be tough!).