I'm six months into clawhammer and -- probably a slow learner -- am just beginning to add drop-thumb notes. From the beginning, I used my 2nd finger as the frailing finger, although for double-stops the ring finger sometimesr likes to pick down simultaneously. But now, as I'm bringing the thumb down to catch those tricky little 8th note "double thumb" notes and fill out the sound, just like you good players do, I'm noticing that somebody's not pulling his weight. There's my index finger, riding along and doing nothing. So I'm wondering why this unused finger couldn't step in and get the drop-thumb notes (or at least some of them sometimes) by picking UP in alternation to the 2nd finger's nail driving DOWN on the downbeats. I wouldn't say it comes naturally, exactly (in fact, it's still very awkward, like any new thing), but after the frailing nail has picked DOWN, the extra finger can pick its UP note without making a large movement, since the hand is already rising. Thus, there's the potential for efficiency.
I've experimented enough to see that the technique might eventually go smoothly. Does anybody add "drop thumb" notes this way? The obvious questions: What's the point? What's to be gained? Well, the technique leaves the thumb free to stay on the 5th string or to explore other possibilities; but what those possibilities might be... at this point I couldn't say. Maybe I'd find the finger would catch drop-thumb notes merely in some cases and the thumb would still do the lion's share.
I'm not advocating, just asking. Again: does anybody play this way?
Riley