With the metal wilton tin you have to let it come back to room temperature to get the shell out. Just let it get back to room temp, turn it over, tap it a few times on the surface and it should fall right out.
I usually make a couple of 4" rounds and a couple of 6" rounds and layer them in the shell, I then carve the top out of a couple of 8" rounds and a couple of 6" rounds (all my layers are 1" tall).
HTH
