My power steering pump started making a new to my car squeeking type noise a couple of years ago. It was cleary the PS pump because the noise started and stopped based on steering wheel position. If I recall correctly, it made the noise when steering wheel was in the centered position and went away when you turned right or left.
I found out the price of the pump (ouch) and did the turkey baster thing to replace the fluid with fresh ATF. Noise went away. I had never replaced the fluid prior to this. The original fluid was very dark and the viscosity seemed very low: very thin, almost water-like.
I have since replaced the fluid using turkey baster several times when I change the oil or ATF. I just pile rags around the reservoir to catch any spills. I have probably put three or four quarts through the system now.
I know that you can disconnect lines and all that, but since rubber lines sometimes develop leaks after detach/attach, I've stuck with the baster. I have one with a needle, which allows me to get deeper in the reservoir.
It also gives me something to do while I'm waiting for the oil to drain out during oil change. It also gives me something to do with the half quart of ATF left over after a AT fluid change.
jim