Black paint is the least durable of camera finishes, and, back when these cameras were new, you paid a premium for it! This is why pristine black "vintage" cameras are worth a premium, now. Every wannabe pro with a few extra dollars bought one.
To renew the finish, take the camera apart and begin by stripping the paint off all painted parts. Get your tiny planishing hammer and miniature dolly and repair all the dents and bruises. Dents which can't be raised and roughness from abrasions can be leaded. Spray a coat of primer, bake at about 140f, and rub out any flaws. Spray, bake, and rub a second coat. If this coat is flawless, you can spray and bake a couple finish coats of black. Fill any lettering with the appropriate color lacquer stick and reassemble the camera. Then, never use it because with very little use it will brass all over again.
Or, you can just live with the honorable scars of several decades use. Personally I stick with chrome cameras.