As much as it pains me, I must disagree with m'learned friend, dragonfly6.
I don't think there's much, if anything, to be gained by doing an hour in a sim before CTC phase 4. It would be, in my opinion, an unnecessary expense.
The instructors at phase 4 are, as far as I know, looking for "trainability" and capacity. If you can show that you are willing to learn, and that you have the ability to absorb information in an unfamiliar setting, you'll be fine.
Fancy going to Furnace dragonfly6? See you there in five :P