I am making a tire cake for my cousin's birthday. I wanted to have a nice smooth buttercream side and then score the tire design. Do I smooth the cake, let it crust, do the Viva trick and THEN score it? Or is that too late? Do I have to do the design before I let the cake crust? TIA!

I recommend letting it crust before doing any design work. Otherwise you take the chance of losing the smooth finish effect you want to keep. JMO