1. Make sure the buttercream-covered cake is totally cold when you're stencilling on it or the icing on the cake can stick to the stencil.
2. Stencil each tier individually before stacking, then refrigerate them to harden the stencilling before you stack the cake.
3. If you smear something, don't try to remove it before refrigerating the cake. Hard icing is easier to deal with than soft icing.
4. Clean and dry the stencils well before you use the stencil a second time on the cake. If the stencil is wet it can make the colored icing run around the edges of the stencilled shape.
5. Do the stencilling, then refrigerate the cake. When the icing is hardened, go back and use a knife or another small tool to remove any icing that's in the wrong spot or to neaten up edges.
6. Try to keep the icing relatively thin on the stencilled part, or it will be more likely to pull off when you remove the stencil. It has to be thick enough that it leaves an opaque coating, though.
Kara Buntin owns A Cake To Remember LLC, custom wedding cakes in Richmond VA