I'm wanting to know what kind of buttercream is the best to use to get it very smooth on the cake. Right now I'm in the Wilton Course 1 class and the icing they have us using gets pretty crusty and it's hard to smooth out to be very smooth once it sets up a bit. I like the idea of using a buttercream with actual butter but wasn't sure if the IMBC or SMBC would be a better option. If so, are they easy to work with and is there any special techniques needed to use this type of icing? Any suggestions or advice would be greatly appreciated.

i just recently started using sugarshacks buttercream method and its vrey smooth. i love it. http://www.cakecentral.com/cake_recipe-5313-1-Sugarshacks-Buttercream-Icing.html