I was forced into 3 finger back in 1995... I was in a band that played alot of fast rock songs , lots of pumping 8th note grooves. Anyway,The day of a big show I sliced open the end of my middle finger, I tried everything I could to make due with the injury.. But it all failed... So on the spot my ring finger just took up the slack and tried to compensate.. It was strange. After that I tried many different ways to make 3 work...
My problem was getting a pattern of 3 (fingers) to work against 4... typical subdivision of musical notes.... because lets face it triplets are easy even with a bad 3 finger techique.
what I finally came up with was playing consistant Ring, Middle, Index....
each time making the next finger in sequence acccent the 1 of the 4 note group..
ring, middle, index, ring
middle, index, ring, middle
index, ring, middle, index
I practiced making sure the the 1 of each group got the accent. Doing this kinda tricks the ear into not noticing the subtle differnces between the tone each finger has naturally...
anyway... I made a very simple video awhile back for a student.... maybe it will help you, or better yet maybe it will spawn a new idea for you, which I always encourage...
Have Fun...
http://www.youtube.com/watch?v=ZVRCqJfAqoQ