1997 radiator flush

The wife has a 1997 4runner. It has major problems when the radiator gave out, and mixed the tranny fluid with the coolant. I have everything repaired, but now am still trying to get the pink sludge out of the cooling system. I have been draining the radiator, then flushing, then draining, then flushing for two days now, and still am getting pink tranny fluid out. I will change the thermostat and put in fresh antifreeze when I am certain all tranny fluid is out of the coolant. Does anyone know of a way to flush the system once and for all? Thanks.