I just did the "suck and fill" of the power steering reservoir as well, except I kept the engine running the whole time. My understanding is that when the engine is running, power steering fluid is flowing through the reservoir constantly. I used approximately one quart of Toyota T-4 AFT. I stopped after 5 or 6 times (of suck and fill) when the fluid became pink and clean.
(car: 1993 LS)