While going to cake decorating school, our teacher gave us this recipe I , have been using it since and it works great and so much cheaper than those you have to buy redy made.
flour (makes no difference self rising or all purpous)
Mix equal amounts of all the above.(ie) 1/2 cup oil, flour ,crisco, 1 cut oil, flour, crisco ) As much as you need that will keep for 2 weeks, Mix well, can be used if lumpy but better if mixed till smooth. Apply with a papertowel, paintbrush or instrument of your choice to the pan you are using, like you would normally coat. Your cake will slide right out and not stick. Hope this helps bring the price down on the many things that we use to do our favorite things, Cake Decorating.