I sweat a lot too.

I found that thin, quick dry clothing was the key.

Especially underwear. They dry extra slow since they are covered by shorts.

I also found that a bathing suit with a mesh liner makes a really good substitute for shorts and underwear.

Ps: Polyester isn't usually scratchy feeling. If it's rubbing you raw, it's probably from salt build up. Rinsing your hiking clothes out with water each night will probably fix it.