Here's an exercise I got from Mr. Vai for developing finger independence and strength. Split your fingers into pairs of two(index&middle,middle&ring you get the idea) and trill between them for one full minute. After you can do this easily increase the stretch between each finger or add another 10 seconds to each drill. I've built up to trilling for two full minutes between each pair without rest, but beware trying to push yourself too much! I gave myself really bad wrist pains trying to build up too fast, so take it slow.

dimebag used to do this before a show to warm up. trills and big stretches for a few mins.

ahh good call I am going to put this into my warm up sessions.