What is this thumb/ index finger approach? I learned something that was in the back of a book of American Folk songs years ago where you play bass notes and runs with the thums and scratch your index finger down and up to play the chords. Is that the sytle reffered to here?

I tend to use a flat pick now but I still use that method sometimes although I have never been able to get into bluegrass music. I can listen to it for about 20 minutes and then I start to get bored with it even though I have seen some incredibly skillful bluegrass players.

Jon