I have watched countless videos and from what I can tell I am doing everything write but my fondant is still not coming out looking the way it should. The buttercream gets mushy underneath and then it gets the fondant kinda mushy and it never sets up right. I have started using MMF and I am not sure if that is part of the problem. The steps I am taking are stacking the cake and cutting the sides down to make sure they are straight and giving me a small space between the cake board and the cake and then I crumb coat the cake and then ice the cake out to the cake board using a bench scraper to go around the sides up to clean up the extra buttercream. I then put the cake in the refrigerator to firm up and then I roll out the fondant and once that is ready I apply it to the cake and smooth it. When I am smoothing it it is ok but then after a few minutes it is like the buttercream gets mushy and then when I am using the fondant smoother the buttercream starts to come out of the bottom between the board and the fondant. If any one can tell me what I might be doing wrong so I can get my fondant to look clean that would be great.

Love your work. I haven't tried to cover with fondant yet but the only thing I can think of is you may be using to much buttercream. good luck and keep up the good work.

I don't work with fondant too much, but I can guess that you are probably using too much buttercream. As you start smoothing the fondant, the buttercream underneath has had enough time to come to room temperature again, so it gets "mushy." I would suggest using less buttercream and seeing if that helps.

AThat is what I was thinking as well when the buttercream comes out the bottom but from everything I have seen they were keeping it even with the cake board at the bottom and that is what I was doing and so I was not sure if there was something else I was missing. If I go less buttercream and the cake is not at the cake board then there would be space in between the cake and fondant and so what is there to fill that space?

Just from a quick glance, it looks like you are using too much buttercream - and your fondant is a bit too thin.

What is your buttercream recipe?  That could be the culprit as well.

I use edna de la cruz's  crusting buttercream. Just 1/2 shortening, 1/2 butter, 4 cups of powdered sugar, 2 Tbsp milk, 1 tsp vanilla and 1 tsp meringue powder.