i powder my hands and the keyboard really well before a performance ( to a point where the black keys look all whitish )-and i always make sure that there is a small container full of powder hidden in the piano for more application to the hands and keyboard in between pieces.
for me it's not to dry the hands per se, but more to make fingers easily slide in and out the keyboard-to get that nice powdery, smooth, slidable feeling between the finger tips and the surface of the keyboard. slide....slide....slide....
and what powder? well, whatever, really. i found HEROCYN medicated skin powder, and been using it since. seriously, and i don't have skin problem and i always smell macho btw...

tds
ps. proof of powder application before performing: