Is the slurry or dust getting on you? I get tiny bumps between my fingers after sanding epoxy. They are itchy but pretty benign. A friend of mine gets what you described on his arms; a sore rash. It would flare up any time he got near epoxy sanding dust. Duct taping his shirt sleeve cuffs to his wrists didn't help You can get Tyvek shirt sleeves or an entire Tyvek suit. Raka sells the sleeves. The full body suits are probably available from auto body supply stores. If you live near a medical school you can find them at a laboratory supply. My wife had one for her gross anatomy class.

Some builders are more sensitive to certain brands so you might try something different on your next boat.