Can you clean rear brakes to make them stop squealing?

Cleaning rear (or front) brakes will not eliminate the squealing noise. Some brake pads have wear indicators which are thin blades of metal embedded into the pad that contact the rotor when the pads are worn down and need replacing. This contact makes the squealing sound.

If you are able, visually inspecting your brake pads to determine if that is the cause, and replacing them if needed will eliminate the noise. Some vehicles' wheels make accessing the brakes difficult. If this is the case, you can take your vehicle to a tire shop or mechanic to have your brake inspected.