Which finger did Stringbean use?

Does anyone recall if Stringbean used his index or middle finger as his primary finger? I tried looking in this thread (http://www.banjohangout.org/archive/96876) but had no luck, I found that Grandpa Jones used his middle and may be the same for String.

However, Stringbean does use a lot of the "floating pinky" method and would lead me to believe he would of used his index finger + floating pinky as it would be easier. Although String was a great player, he could of learned middle finger + floating pinky.

I've tried observing these videos- its just to hard to tell.

http://www.youtube.com/watch?v=8uOy3WdT3mY

http://www.youtube.com/watch?v=eOagiZ3YTsY

http://www.youtube.com/watch?v=BgjzlvvD_7s

Anyone else know anything? Thanks