The only ways to cycle fluid out of the converter is to physicly drain it or while its running and flush a lot of fluid thru it.
I you are going round after round as in a big buck bracket race then a fan cooled cooler is a must, otherwise a cooler is a waste, I would rather keep the motor cool by not running it between round instead of makeing heat just to change tranny fluid.
Good fluid stays consistent going rounds as long as time between runs, But late in the day when you pic up your time slip and they tell you that they need you back in staging for the final round, Not much you can do at that point