Tim Commerford, he of Rage Against The Machine and Audioslave, said in a recent interview that he uses the Jamerson one-finger approach most of the time, occasionally adding a second finger when needed, on faster passages.
I'm strictly two, occasionally leading with one finger. I do a fair bit of raking in my playing just to add colour to it and that's one-finger business. I'm self-taught so I don't have any tips as such, but I can say that I just sat night after night alternating between the two fingers picking chromatics and scales until it was...um.....deep and crisp and even, I guess. Somehow, it became intuitive to me and I jump in and out of one and two fingered approaches so often that I barely think about, it or even notice. But I lead with two for the most part.