lay the fiberglass on the back of the hole, this way when it drys it will be a backing to the bondo and give the bondo something to hold onto and keep it from breaking away. get the whole cloth wet by dipping the entire thing in the mixture.when it drys it gets really hard and stiff and thats what you want. if you get any resin anywhere it'll sand right off, you might have to smooth out and trim the fiberglass with a dremel and some sand paper once its dry too. also while its drying make sure the part at the hole doesnt bend into it, try to keep it flat there. its hard to describe but i hope it makes sense