When I first saw Norman Blake play (late sixties or early seventies at Bean Blossom) he was using the thumb and index "flatpicking" that Rick is talking about. He came on stage as part of someone else's set and just blew everyone away.

The "Nashville Cats" that use the flatpick plus fingers technique aren't usually playing straight melodic lines, they're usually playing complex backup and puncuation licks that require the particular attack one can achieve that way. You don't see acoustic players using the technique as often as the electric players.

Also, I seem to remember watching Chet Atkins use his thumb pick as a flat pick for both down and up strokes. He didn't play a whole piece that way, just a few notes or bars.

      - Mark