I did my steering fluid change every 48k ~ 60K km. You have to flush the power steering system to get the old dirty fluid out of the system.
Repeat step 2 ~ 5 till your fluid in the reservoir is clear and pink (all new steering fluid should be clear and pink) and sees no foams on the fluid the pump sucked up. The old fluid is brown, dirty and foamy. Leave the engine turn on all the time, so the power steering pump keeps pumping the fluid through the line and system. You don't have to worry about air gets into the power steering system. It's not like flushing brake fluid. The air in the power steering pump will get push to the reservoir when you turn your steering.
Hope this will help. :smile (2):