I am making a cake this weekend for a little boy's 2nd birthday. It's going to be a Thomas the Train cake, and I want to use a GOOD buttercream icing with fondant on top. My question is, what would be the best recipe for this? Do I want my icing to crust first before I add fondant? Or do I not want it to crust at all? And, finally, what recipe do you all suggest? I have looked at the recipes here on Cake Central, and the "Rick's Special Buttercream"looked pretty good. Would that work?

I know that was a lot of questions, but I want this cake to turn out perfect, and all you Cake Central users never let me down!

If you're using a crusting buttercream, yes, you want it to crust before adding fondant. That will give you a nice sharp clean edge to your fondant. After my final coat of icing I wait for it to crust firm before adding fondant.

Before adding your fondant you have to use something to get the fondant to stick to the cake. I use simple syrup (mix 1 cup of hot water and 1 cup of sugar) and paint it on with a pastry brush. PLANET CAKE has a great tutorial on youtube showing how to do this. It doesn't take very much just paint on a very light coat.
Some spray on a fine mist of water but I'd rather use the syrup. I don't like using water where fondant is concerned.

Indydebi's buttercream is my favorite buttercream receipe. It taste awesome.

I prefer IMBC, which doesn't crust, tastes fabulous, and works wonderfully w/ fondant. It is not super sickly sweet like crusting frostings, which makes it even better w/ the fondant, which is super sweet itself.