Don't force the fittings on the A/C system. Many of the fittings are made of aluminum on one side and steel or brass on the other. The quickest way to strip the threads is to force it. If you can get the fitting out of the Jeep, put it in a vice and hit it with a hammer simultaneously on opposing sides. Repeat while working around the hex until it turns easily. By doing this, you loosen the oxidation that forms between the two different metals, and are more likely to get it apart without damage.