Kawzak,
Since you got started down this path by your dealer, you're probably going the right route by following through with the ATF+4 conversion.
Since I last posted on this thread, I did a drain and fill with the Valvoline MS5931 certified fluid. I combined both methods. First I pumped out and refilled the pump reservoir as kawzak stated. Then I pulled the return hose and ran the engine for 3 seconds.
Please be advised that the "low pressure side" return hose still has reasonable pressure and very high volume, especially when the hose flexes out of the bucket under pressure. Fortunately, cleanup was facilitated by my wife's discarding a bunch of large old bath towels into the garage rag bin, my epoxy floor covering, and some brake cleaner I had handy.
Anyway I think my flush method both fastest and most thorough, because on one 3 second run the rack gets all-new fluid from the pump, and dumps its old out at the same time. I would not call it easy, though. Even if I had avoided the mini-Valdez incident by using a weighted-down bucket and securing the hose with clamps, I still had to cut off the old hose and then dremel-cut off the end and its clamp.
Now that I've done (what seems to be) a complete exchange, I'm going to maintain it more often using the pump from the top method.