Regarding the so much talked-about use of three fingers with the right (plucking) hand, here's an exercise that worked, and still does for me. It's just the same old broken thirds exercise but played with three fingers rather than the usual M-I pattern. The good thing about this is that you get to practice two different patterns: M-I-R ascending R-I-M descending you also get to work skipping/alternating strings rather than doing the usual tripplet-like pattern on one string. I think that what helped and helps me a lot with this is that I come from studying classical guitar technique, which makes plenty of use of the ring finger along with index and middle when playing arpeggios, which are also played with several fingering combinations. Hope this helps, if so, I'd like you guys to let me know. Regards.