Dan,
I strongly suggest that you look at the alternate method and use the upper hose.
It is much easier to reach and you do not have to remove and replace the battery several times ( to start the car to pump fluid). Many of us have used the upper hose with a 1/2" ID hose over the end for a drain with good results. The concerns voiced about flushing the cooler can be addressed by blowing it out with some low pressure air blown into the cooler where you disconnected the upper hose. Do this before starting the flush cyle. The fluid in the cooler will join the fluid you are pumping out of the sump. BTW, getting a wrench on the lower hose connection on the tranny can be a PITA.