My viola playing and teaching comes from a relatively short line of amazing violists. I will eventually get the whole story up on my website, but I've been so swamped lately I haven't had the time. The very short story, though, is that Karen Tuttle taught a generation of violists to be comfortable and as natural as possible while producing seriously beautiful viola sounds, and then I learned from many of them.
One of these techniques is dubbed the "release and plop" (at least, that's what Carol Rodland called it), which is a description of how left finger action can and should work... instead of squeezing fingers into the fingerboard, one lightly taps fingers onto the string, producing a round, beautiful, and cleanly articulated sound, while being very relaxed.
I taught the "release and plop" to several students today, and each of them seemed a little blown away. How amazing that viola playing can actually be comfortable and relaxed!
Happy practicing... you know who you are. :)