ZOF:
Consider getting one of those Prestone Flush kits, and use a short piece of heater hose to install the flush T temporarily into one of the heater lines. Then flush it until the water comes out clear.
Another thought. When you go back in with the new AF, consider the Preston Global amber colored GO5 coolant that is lifetime rated.
I agree that the Dexcool is problematic, but I will run it while my GT is under warranty.
Once that is done, I will make the switch to the GO5, and not worry about it.
Good luck Don