Holy Buckets... I can't even imagine trying to smooth all that out... good luck with the fiberglass though that was super time consuming for me. Have you considered using Rondo on any of the pieces ? it would be a lot easier to get inside the spikes and any part that is detailed. The fiberglass is a lot stronger, but in areas that don't need that much strength you might want to consider doing that. Rondo can warp stuff pretty bad too, so I usually coat the inside with at least 1 coat of resin before applying Rondo.