[spdbrake]

Adding another hole to the cavity with allow air to cycle thru the area. Not fast mind you.
What works best is add a 3/16" or 1/4"drain line to the new hole and have it hang below the car where air will blow across it. Scarf cut the end at a 45deg. Face the opening towards the rear of the car. Air flow will create a vacuum effect due to the scarf cut.

Another cleaner looking way IF you have Sceet tubing already installed for brake cooling is: Insert the drain tube into the brake cooling hose, ensuring the Scarf cut is facing the brake side.