a 4 or 6 oz. rawhide mallet will work-they are also on Ebay and leather stores sell them
Use the mouthpiece puller to put pressure on the mouthpiece, then tap the mouthpiece receiver lightly with the mallet. Tighten the puller a little more if it doesn't come right out. Tap again, it may take several times to get them to pop. Don't tap so hard that it might bend the lead pipe.