If you poke around on YouTube there is plenty of close up footage, including his appearance on Pete Seeger's TV show that really lets you see what he was doing.
Also, there is quite a bit on him in the PBS American Epic series mentioned in a recent thread. I think it is episode 3, about 2/3 of the way through the show.
Playing his tunes is very enjoyable. Playing them just like he did is not something I'm qualified to comment on
