I have done this project myself. If you get some white spirits ( I think it would be called mineral turpentine in the US)it can help to thin out the silicone so its easier to pour. If you have found anything that says to add corn starch to it DONT. it makes it brittle and the mould just breaks really quickly. Also if you use a paintbrush to first brush on a thin coat to your item and then pour the rest over it it makes it less likely that you wont get air bubbles.
Anyhoo HTH with your project. Have fun
I DID see a video with cornstarch. I was going to pick some up. Someone (dixie?) posted a link for a video where they use dish washing liquid to work with the silicone, but it's still a mass. That just makes it easier to work with as a dough like consistency. The cornstarch looked less messy. Thanks for the info!! I'll go back to Ace and see if they have that stuff. I think it's called mineral spirits, but I'm not 100% sure. (I remember my mom using "mineral spirits" when I was a kid to remove oil-based paint. I don't think there was latex back then. Or if there was, it was too expensive for us.)
I'll post the molds if they turn out OK. I'll probably post the molds if they're a fail so we can all laugh at them.