I respectfully disagree a bit. The debris (like metal shavings) is suspended throughout the fluid in the system.
With a rack installed, I disconnect the return line at the PS cooler (it goes from the cooler to the pump) and put it in a bucket. I start the car and add fluid into the reservoir (as old fluid is spit out the return line and into the bucket). Once the fluid coming out is clear, I reconnect the line and fill the system. Then purge the air and top it off.
Just how I see and do it.
Good luck.