An amazing build and even better finished piece, the rub and buff really worked out well!
As others have said for the powder you can brush it into the mold and cast which will still give you a good effect. I am still trying to wrap my mind around the tape method, namely the tape itself, as any tape I can think of seems to be too weak/flimsy to be able to hold up to the silicone or am I wrong? I am eager to give this method a go as I hate smoothing clay.
If you do anymore molding in this fashion it would be great to see more pictures