Most often a 12 point socket will work. I've taken keys that are close and ground the non fitting portion off. At times I've had to air chisel them, catch a notch in the grove and walk it around. Also smack inward towards the wheel with a large hammer,many times this will loosen it enough to use the previous socket idea mentioned. I've had to torch them off as well. Covering the surface of the wheel with wheel bearing grease before torching will protect the finish of the wheel.
Good luck Doug