Ya, I think the easiest way is to rub your pants before you shake hand with them (but no so obvious lar)

I used to have the sweaty palm problem like you when I was young. I tried a special treatment and It works....now I don't have sweaty palm anymore.

My special treatment (Forced by my mum when I was young) : Rub our palms by putting few cockroaches in between our palms for few minuites. It works for me....maybe you can try it out.