510, unfortunately our laptop is a bid dodgy at the moment so I'm using a little netbook to surf. If I blow up photos the resolution is really bad, so I can't say for sure what it is Barbarin is holding. It does look like some kind of fly-whisk, though. It could also be a whisk broom held sideways and we're not seeing the flat of the brush.
Either way, it ties in with my findings. As I posted on the redhot message board, whisk brooms were used (at least in Chicago) before wire brushes were, although this is the first instance I've seen of one being used with a snare.
As he's holding the 'brush' in his left hand, he was probably sweeping 2 & 4 with it. Regardless of what hand drummers used, they'd switch to a LH sweep so that the right could do other things. In the 20s, the RH would often play the bass drum - note that Barbarin's RH shoulder is dropped. Ben Pollack used a fly swatter to beat out time/circle with the RH on the bass drum; LH sweeping 2 & 4 while he did so. Other players used a mallet or stick in the RH. There's a really racist (as in jaw-dropping) Betty Boop cartoon featuring Louis Armstrong, from around 1932/1933 - I think it's called I'll be glad when you're dead you rascal you. IIR, the drummer was Tubby Hayes and for a brief moment you see him doing what I've just described (although it's unclear exactly what he's playing with the RH, because the bass drum obscures it).
Re tapdancing. The Chicago drummers seem to have all adopted the press roll technique, so that's how they ended up playing brushes. Before that, or in other areas, who knows? 'Circling' was in use during the 20s (as described above), but I can't find any examples on record (there is film evidence). What is certain is that a huge amount of drummers from the swing era were also 'hoofers'. I’ll find the list later and post, but it's surprising how many could tap dance. It goes without saying that one discipline must have influenced the other. At the end of the day, sand-dancers and brush players were trying to create rhythm using swish and the moves could be pretty similar - some used their feet, others their hands I guess…