I always had hand sweating problems: hyperhidrosys. It is possible to cure this (in a chirurgical way, etc.) but it costs a lot of money. So I wash my hands with Marseille soap (the real on, not the liquid one) before playing bass and it helps me to sweat less, and somedays, thaks to the Marseille soap, I don't sweat at all. It might help you too. But if you never sweat like today, you should go see a doctor, shouldn't you?