I have used both spray release and baby powder over the past several years. In my opinion, the baby powder does just as good a job of being a release agent as the spray release. Make sure to use one of the two methods though, to prolong the life of your mold. I've had multiple occasions where i stopped using a release agent because I ran out or I simply didn't feel like taking the time to apply it to the mold before pouring the resin, and after a few castings the silicon drys out and the mold will eventually rip when you remove the casting.