Fiberglass resins come in at least three formulations, polyester, vinylester and epoxy. Polyester is the least expensive, but also has the least amount of adhesion and can delaminate easily. Both vinylester, used in a lot of kit airplanes, and epoxy (used in boat building) can be used as resins for fiberglass cloth to coat the foam.
There's a method using foam to make kit cars at
http://www.rqriley.com/frp-foam.htm that shows some of the process.