take the torque converter to a local transmission repair shop , they will have a machine to pressure flush the converter,
but don,t be surprised if they tell you you'll need a new converter,
after all they can not charge nearly enough to clean the existing converter to make enough profit to compare with selling you a new converter,
and then they can clean yours, paint it,
and sell it to the next guy.
if that sounds a bit pessimistic.. its just 50 years of dealing with local transmission repair shops.
obviously the time lag between the contamination and how long it sets before its flushed maters,
some converters can be rather easily cleaned internally with a power flush,
others are a P.I.T.A. and are generally just replaced, and yes youll need a new radiator or separate trans fluid cooler and most likely the transmission will need to be rebuilt