I was using smooth-on resin, it is nice but it's short shelf life turned me off and would get very porous parts. I guess vacuuming or pressurising would help with but they don't tell you that. I still like their mold rubber. I can get smooth-on locally from an art store for very cheap but the alumilite I have to get from the company itself and the shipping across the border gets you, but it has a long shelf life. I've been trying to get that store to bring in alumilite. I also was never trained on it just learning as I go. Both are good in their own way. I see the pictures of smiling casters with gallon sized amounts in massive molds and wonder how they do that without it hardening while pouring.