For my power steering fluid, I used a turkey baster, drew out what fluid I could from the power steering resivoir (it is pretty small inlet diameter, check it before getting one with a opening to large) and then add new fluid. After a couple of times, then much of the fluid has been replaced.
From what I have heard, to 'Purge" any air from the power steering lines, you turn the wheel to hard left, wait for it to stop making noise (about 20 seconds at full lock to the left, then right) and it will be ready for use.
Make sure that you do not overfill the power steering resivoir, the fluid expands a lot LOT when you warm up the engine, and can cause problems if overfilled.
Good luck,
Fred.