These are a MUST HAVE for detailed projects. If you want to get the real look of frosting you have to invest in a set of these. Don't use 100% silicone with the pastry tips because you wont be able to wash the silicone out when you are done. If I must use silicone sealant I wait until it dries in the tip and then I peel it out (Tedious and not worth the trouble).
Silicone Sealant -WalMart:
I love the way this looks as frosting because it is very white and smooth. I don't use it for large projects because silicone attracts dirt like a magnet. I do use it to fill some Kawaii pastries I make. Another bad thing about silicone sealant is that it is IMPOSSIBLE to wash it off. If you get it on your hands while it is wet you can't get it off. Water just does not work with silicone. Once it is dry you can peel it off.
This is my favorite frosting to use because it is very detailed and it is smooth enough to use with a pastry decorating tip.
Buy it at Wal-Mart or any hardware store. I don't use it very often because it is really thick, much too thick to squeeze out of a pastry bag. Also it crumbles and I do not like that. But it does have it's place as a frosting, I just have not decided where yet. :)
Puffy paint is a good frosting for some things. It is much too wet to use in a pastry bag. It wont keep its shape very well because it is too wet. Like the Spackle, it has its place as a frosting but I don't know where!