How do you get a rusted hitch out of a receiver if nothing else works?

Apply a fixed load to the hitch (block tires if using a trailer or properly attach a chain or strap to a solid object). If using a chain or strap, wrap the hitch in a suitable towel. Make sure that the area in range of the hitch popping out under pressure is clear and protected as needed—particle board or something similar can be used behind the chained hitch to protect the area from the hitch. Note that a towel is not needed if the hitch is attached to the receiver of a trailer or other load because the hitch ball should be locked into the trailer tongue.