So not too long ago I posted a topic on what to do on the cake I'm planning for my daughter's birthday. I'm doing a Draculaura doll cake using my wonder cake mold. I plan on using fondant to create the look of a flowing ballgown. This is the video I found that shows how to create the draped look I am planning on:
http://youtube.googleapis.com/v/8cGUQcikzEY?autoplay=1&rel=0&enablejsapi=1&playerapiid=ytplayer

I was just wondering if anyone thinks it's necessary to use piping gel on the cake to get the fondant to stick? I was just planning on using straight Swiss Meringue Buttercream. Will draping the pieces on just the buttercream work to still give me the look I'm looking for?

It looks like that was just used to make a fondated cake sticky. I'd just put it straight on the buttercream and not think about it, so you should be fine.