I've been doing this for years-but on older GM cars mostly with the THM400. I get the flare wrench on the radiator fitting(upper on these)and after removal of the line, push a hose over-snug fit-and direct the hose into an old gas jug. I start the car and idle til I get about 4 quarts out-doesn't take long! Shut off and replace with fresh ATF in the amount removed. This on cars I've owned for years and already know the condition of the transmission and filter. The more recent autos with the 'interesting' line fittings, I haven't done tho-good luck. Dan Mpls. Mn.