I purchased the Maggie Austin ruffle cake tutorial on Craftsy and want to do it on top of a buttercream covered cake instead of fondant.

In the questions from students she says that she doesn't think it will work, but she uses SMBC. I use SugarShack's buttercream recipe and it crusts well and gets firm when cold.

Has anybody used her technique on crusting buttercream with success?

no, I haven't tried it in buttercream but I did read somewhere on here that it was possible to do it in buttercream

You can do it on buttercream, I do ruffles on buttercream every time I do a ruffle cake. Here: http://acaketorememberva.blogspot.com/search?q=ruffle+cake

I don't do it upside down like she does, but you could do it that way and it would work the same.

Thanks so much!

I love the ridged roller for marking the side of the cake. I used a cake comb once to mark the side, but the marks were much farther apart. I'll look for the roller for the next time.