I recently took Wilton Course 3 Fondant and tiered cakes. The instructor told us to ice the cake with a thin layer of buttercream. I wasnt sure exactly how thin "thin" meant. I figured you would want it thicker than a crumb coat because you wouldnt want to see all the lumpy cumbs under the fondant. So I put a coat of buttercream on. Not as thin as a crumb coat and not as thick as I would normally ice it. I guess you could say it was just thick enough to hide the crumbs and crumb coat. So anyway. In class we covered the cake with fondant. When I got the cake home I could see lumps of buttercream that I had to keep smoothing out. We werent cutting the cake until the next night and when I looked at it the one side had bulged out a little at the bottom with a lump of buttercream. So how thin exactly is this coat supposed to be?? Am I just using a crumb coat or do I make it thicker than that??

You may a little bit to much icing....Usually a good crumb coat will do.....I let my set for a while to get a crust on it.......seems to keep the icing in place better.....but go to www.AtecoUSA.com there is a great tutorial on applying fondant.... it helped me alot.