yep, pitchers/bowlers use a rosin bag. rosin keeps your hands sticky so you can keep a grip on the ball (or whatever) and not recommended for yo-yos/tops. it's the same stuff band geeks put on the bows of their string instruments. it's basically resin from trees and plants and similar to sap. wouldn't want that on my hands.talc (or talcum powder) would be alright...is the same stuff that they put in baby powder. baby powder may also contain corn starch. people who play billiards may be familiar with hand chalk (which is not actually chalk, but talc - real chalk is calcium carbonate and rock climbers/weightlifters/gymnasts use magnesium carbonate, which is close) which is used to keep hands dry. incidentally, billiard players also use billiard gloves instead of hand chalk, which some yo-yoers use.i'm full of useless knowledge.
salut BMC ! (best medical crook?)for sweaty hands there's an unbeatable trick it's a gujarati posture (india) easy to performjust sit , with your arms raised to a waist level positionthen put the thumb nail in contact with the tip of your pinkiespress a little not too much just enough to feel your heartbeatafter 30 sec or so you should feel your heartbeat in both pinkies and the sweat starts to slow down.. then you concentrate a little for about 3 mn and the sweat will be gone , wash you hands after the process, and go straight to the stage jim