I plan to crumb coat and fill my cakes with SBMC and then cover with fondant. Do I need an icing dam? If so, should I use a stiff buttercream? Or can I thicken up the SBMC? Thanks for your help in advance.
Not necessarily. When I fill my tiers with the icing I'll be using I never dam, I just don't fill right to the edge, I leave about a 1/4" margin.