I just posted my buttercream recipe. You will get sweating at some point during the defrost, but it usually doesn't happen until after the cake is fully iced. Icing a cake should be a rapidily done task, if you move too slowly you will have a problem, not only with the icing forming condensation prior to the cake being fully iced but then you have the huge crum factor, especially with chocolate cakes, it can tear up hugh chunks if the cake is defrosted fully when you try to ice it after using the most moist cake method.
After you ice the cake allow it to fully defrost and the sweat to naturally dry before decorating, or if covering with fondant, do so immediately after icing, actually after you ice it before covering with fondant refrigerate the cake so the icing is set, then cover with the fondant.