Your plane is incredible. I don't come over here often but it sure was nice to see those pics.
I assume you're talking about polyester finishing resin? I did one plane with this stuff many years ago and the overwhelming disadvantage with it is the smell. The second I cracked open the can I had a headache. However; it is very hard and I think I may start using it again because the epoxy's I've been using dent way too easily. I've never made any fiberglass parts using it so no comment there. You can use Bondo from any auto parts store or even Walmart. It's probably the cheapest polyester finishing resin available.
carl