I am getting ready to carve 2 6" and a half 6"ball into a football helmet. On my practice one I covered from the top and cut away the fondant that would be on the inside of the helmet. Then I cut the piece and added it. Here is the problem. I couldn't get the BC smooth enough, and my fondant was a little misshapen. Should I use alot of BC or just enough to hold fondant?
I am far from the best decorator but I can tell you that you need to use a light coat of buttercream under the fondant, similar to a crumb coat. If it is too thick it will glob up under the fondant. However, if it is too thin the fondant also will not be smooth.
I've learned my lesson about this. The one time I did a thick coat of buttercream, my fondant started to slide down the cake and I could see every bump and crease under it. So, now I use a thin crumb coat - just enough to keep the crumbs at bay and hold the fondant onto the cake.
Make sure your fondant is thicker. I have found that most people roll it thicker and have better results. I only roll the fondant thin for detail work. Anything that covers a cake gets about 1/4 inch thick fondant. I like to use a good layer of BC because I don't like the taste of fondant.
I agree with smbegg... I hate the taste of fondant so I always put a nice amount of bc under it....if your bc is super smooth, then it makes it easier to have smooth fondant...