Grinding fiberglass sucks anyway you do it. you can get the coveralls from home depot for about 10 bucks, they are made of tyvek. they are thin and will keep most of the fiberglass off you. Once you do have fiberglass on you the worst thing you can do is get into a HOT shower it opens your pores up and the fiberglass grabs harder. What I learned over the years from all the fiberglass guys is panty hose rubbed across your skin in a cold shower pulls the majority of fibers off you. It may sound funny but it works. do yourself a favor and invest in one of these if you have a good amount of grinding and cutting of glass
http://cgi.ebay.com/3M-7800S-Full-Fa...QQcmdZViewItem
It keeps your face completely clean and your breathing clean air.
you will never wear anything else after you wear one of these for cutting, grinding, sanding with a DA and shaping of fiberglass and putty. They also are extremely comfortable to wear.