I read through the tutorial on the FBCT, but was wondering: what consistency should the BC be? If I want the outline to be the same color as the fill-in, do I use stiff consistency, then thin of the same icing or something else? Hoping to practice it this weekend for DS's birthday cake.

I use a soft medium for all of it.

I think the outline color all depends on the picture. I have outlined some with the same color and I have outlined some with black or another color. It just depends on what you want the final product to look like.

From my own experience, royal icing hold ups better for the outline of the Buttercream transfer. I have also used fudge for the outline of the BC transfer.
If you use black food colored buttercream , there is a chance that the color will bleed onto your other colors when your BC transfer defrosts on your cake. Thanks,

Yoli

I've never had my colors bleed (even the black) when it defrosts.

I agree with TexasSugar - I've never had my black bleed when defrosting. I usually do my FBCTs on a metal cookie sheet. I do my outline first and pop it in the freezer until it's really firm (I usually leave it for an hour or so - depending on how much time I have), then I do the backfilling. It really helps keep my outline from "walking" on the wax paper. Good luck!

Just did my first one the other day and it was pretty easy! I used a medium consistency bc for all of it and didn't let the outline "set" at all. It came out perfect (in fact, I'm kicking myself for not finding out about the fbct sooner!!).

HTH and Good Luck!!