The faced foam board usually has foil on one side, and a poly sheet on the other. The poly is easily pulled off. The foil, not so easy. I buy it in "folding packs" from the local manufacturer. The resin you mentioned- depending on the chemistry, it may dissolve the foam. That may be the issue you noted with "outgassing" I use the beaded foam sheets, and directly pour 2-part casting resin into rivers and lakes. It does not eat the foam. The only issue is that if you want texture, you have to keep picking at the resin as it self-levels until it is almost set. Alternatively, for the texture I use the Woodland Scenics water texture stuff in the 3 or 4 ounce jars.