You're not alone. I'm a hand sweater too :) I've been playing a lot of outdoor venues this simmer. When it's humid my hand sticks to the neck of the guitar and it's hard to slide up and down the fretboard. I keep a towel handy and wipe it down every chance I get. I also wash my hands in hot soapy water after every set. That's the best advice I have so far until I figure something else out.