I've only had success with the nail trick with Silicone caulk, which does not dry hard like glue. If you use a thick enough nail (or dowel), you can pull it later and still have a channel to dispense the caulk. If the glue will harden into a solid plug, you're probably going to have to cut the plug off anyway, so it's not clear a nail will help.

Is the 4200 catalyzed by moisture, or does it react with the moisture? You might be able to cover the end with plastic or dip it in hot wax, then put the tube in a ziplock.