In extreme cases I am sure these techniques would come in very handy. I find most times resorting to a vise type device isn't necessary. In my experience the force generated across one hand is all that is necessary. It is amazing how much force you can exert between you palm and fingers, as much or more than with your arms in many cases. So if you arrange the pedal wrench so that it is about 30 degrees (more or less) to the "tight" side of the crank arm (how many degress depends on how big your hands are) and grasp both the wrench and crank arm in the same hand or even both hands, you can usually squeeze the wrench toward the crank arm and loosen it even in very stuck situations just by "closing" your hand. Easier of course on the non-drive side where the chain rings don't get in the way. But this does work on both sides. Good luck.