I bedded an old rifle that I had using this:
http://www.autozone.com/autozone/ac...ody-filler/_/N-255s?itemIdentifier=61761

It worked out wonderfully. That stuff can be found at your local Auto-Zone, O'Reilly, Pep Boys, Kragens, & the like if you need some immediately. It is water/chemical resistant and works on wood, plastic, aluminum, metal, etc;

The price is right as well. I also used the paste wax for a release agent. This was my first attempt and it worked out flawlessly. I spent about a week prepping for the actual bedding event, even going through a couple dry runs trying to anticipate and plan for anything that happened along the way. I can tell you that once dry, that is some HARD stuff.