AI'm doing bridal fair in a month and ill be bringing 5 dummy cakes that I want to then keep on display in my shop. I e never made a dummy cake before so what I want yo know is what is the best frosting to adhere the fondant to the Styrofoam that will also be fine left out on a display case for a long time? A shortening based buttercream?

I haven't done a dummy but watching a tutorial found you can use just plain shortening under fondant. It will be interesting to see what others use.

Just rub it with shortening, just enough to make it sticky, don't put it on like you would buttercream.

I just mist it with water, it is like super glue, you have to soak the fondant off if you want it off after the fondant hardens. 

Lol...no. Just put it in a garbage bag, and whack it with hammer or meat tenderizer (the flat side). Cracks right off, and there's no mess. :D

AThanks ladies!

I use shortening - not much and I find I can pull it off in big chunks when I'm finished with it.