I don't know if anyone does this, but I discovered this weekend that using a stiff cake ball "dough" works quite nicely in place of RKT to sculpt small/medium sized cake decorations. I had to make a dinosaur for the top of an 8" round cake. Once refrigerated til firm, I covered in fondant. I did this because I HATE making RKT for any project...I just used the cake cutoffs and kneaded a little icing and the cake together. Voila!
Great to know! Even though I generally use the ready-made ones, they can still be a pain, and it would be good to have something you can substitute unless you REALLY need to use them. I imagine the cake ball mixture comes out a lot smoother, as well, and you might not need to ice it with ganache or royal icing before you cover it to get the bumpiness to go away.