Let it run until it's hot enough then put it in gear to further circulate fluid and top off (just don't try to drive it around) then do the fast relearn. Once the fast relearn executes, take on a short test drive, check fluid after about 500-1000 feet of driving, top off as needed. That's how shops that I work with tell me some of them do it.
For anyone needing it, here are the ATRA Procedures for conducting the fast relearns on these transmissions.
