How thick does it all need to be? Lowe’s or Home Depot have foam you can use. For your purposes literally any cloth or maybe even chop strand will work. Thinner glass will conform to curves better. Heavier gives mor rigidity and build up. You could get away with polyester resin too, just don’t build it up too many layers at a time. It’ll get too hot probably. Polyester cause it’s cheap. I don’t know for sure if polyester will eat the foam but it’s like 1/4 the cost of epoxy.
your question is to vague