Although I've been plunking around with claw-hammer banjo playing for several decades, I feel I never got very far largely because that nearly every time I'd drop my thumb to play a note on any of the first four strings (called "double-thumbing"), my darn thumb-nail, even if cut short, would obnoxiously catch on a metal string & goof up the tune. Nothing I ever tried eliminated this problem, which caused me to pretty much give up banjo playing. I've FINALLY found the answer --- NYLON banjo strings! For some unknown reason, my thumb-nail does not even start to catch when using nylon strings & I now am having a blast working out a lot of the old-time tunes (that I've played forever on the fiddle) on the banjo. In short - putting nylon strings on my 5-string banjo made ALL the difference in the world as far as double-thumbing & banjo playing in general. An added benefit is that (for me at least) the instrument also sounds better, plunkier & somehow more down to earth, using nylon. Give nylon strings a try if for any reason you have any trouble double-thumbing, It made all the difference in the world in my case.