Practically, if the sparkplug is not plumb, with the electrode down, how are you going to dispense any refrigerant liquid onto it, i.e. so that said liquid stays on the sparkplug, and does not migrate onto the aluminum head? Even with perfect-orientation plugs, which are often in deep wells, again, how to refrigerate the plug and not the head? Simply not practical. Good penetrating oil, time, 1/8th or 1/16th turn tightening, and then loosening, a few times... over an extended period of time... and then bringing engine to operating temp... that'd be the way I'd do it.
This pre-supposes you CAN do it over several days.
