what do I put around the dummy cake to stick the fondant on? Is it buttercream?

water/

Shortening.

I was wondering this too... here's a great link http://cakecentral.com/cake-decorating-ftopict-593522-.html&sid=c76ccc551c55fb924defeb9d5c7b28c5 They talk about quite a few different ways, and I didn't even think about smoothing out the top of the dummy cake so it doesn't rip the fondant. Great tips!

thank you all for your responds