How do you clean rust off of a Piston in brakes?

I have a 1992 Mazda 929, and we're trying to get it running again. Right now, everything's good except the driver side brakes are stuck.



I was told by my uncle [who had the car before me] that the Piston inside the brake needs to be cleaned [since it's rusty from sitting facing the street]. I know I need to take the wheel off, and the capilar, but does anyone have step-by-step instructions to get to the piston and get the rust off?How do you clean rust off of a Piston in brakes?if its rusty enough to be stuck,its junk....get a rebuilt or new one from the parts store...years ago we cleaned or rebuilt calipers but today with the price of calipers(they are cheap) there is absolutely no reason to fool around cleaning rust off of a caliper piston...find some other area of your car to concentrate labor on...its just not worth the time