I have read somewhere that someone mentioned that you can use the glue for a hot glue gun. You will need to heat up the glue sticks in a pan so you will need to get a pan that will NEVER be used for cooking again. Once the glue is melted in the pan, use a paint brush and then use the glue in place of the resin.
It won't harden as much like resin, but it might suffice. And since you are trying to get it really hard but can't use fiberglass, I have read in other forums that people are using some other stuff that doctors use for casts, I think. I can't remember the name of it, but hopefully someone will mention something. I don't think it's as dangerous as fiberglass.