You're talking about this one, right?
I bought this at Hobby Lobby also.. a few months back.. These same type of gems were on my wedding dress, so I was going to try to incorporate them into my cake. I couldn't get it to work right. Sadly, I know how to do it now.. Use chocolate, instead of hard candy, so it can be painted silver! haha
At least I got a nice mold out of it, and my cake turned out fairly decent, all things considering.
It's really easy to use, by the way.. Just pour very slowly. Don't be in a rush.. and make sure you have it sitting on parchment, a cookie sheet, a silpat, anything.. Just in case it overflows. I've been burnt many times also, working with hard candy, but I still play with it. It's not bad, once you get the hang of it.
Now, if only I could learn how to do some real sugar art, instead of just molding!!!
**edit** yeah, helps if I add the photo, huh?