Tip of the day.............Gold Bond Medicated powder all over you before you mess with fiberglass, it fills the pores and allows you to wash the stuff off of you when you're done, reduces the itch by leaps and bounds....Also, cold shower, not hot, keeps the pores reduced in size and does not allow the glass to penetrate the skin and give you the deep itch. long tee shirts and duct tape work OK too.
Also gotta have a full face respirator for long term glassing, I use mine everytime, uncomfortable as hell (and hot) but I don't cough for two weeks after sanding either.

Keeps the shit out of your eyes too.
GT