Okay, it's thread creep. So sue me. But it's also an interesting topic.

On the up / down stroke question:
I'm not sure I know of any players who use a thumb pick for both up & down strokes. Wouldn't it be easier to use your thumb and index finger in an alternating pattern to achieve the same result?

Alternatively, I've seen some folks, most notably Richard Thompson, use a flat pick between thumb and index finger then use the middle and ring fingers for a three-finger style finger picking pattern. That would certainly allow for utilizing the flat pick for some pretty rapid runs.

- Sean