Use dex 3 atf. And i would not add anything extra.
What i did was remove the lower hose from the PS reservoir catch the dirty fluid, button it back together and top up. start the car and turn wheel lock to lock, shut down the engine and repeat. i did that about 4 or 5 times until the dirty atf looked clean. I had no issues with getting air in the system, or causing my pump to run dry using this method.