Just in case you look here, I'll offer some advice.
- Use silicone, since it pretty much only sticks to other silicone. Do a small test on the polymer portions. If you're concerned about adhesion, put a small coat of Vaseline over your gun as a release. Clean it off after molding.
I would recommend a 2 part silicone putty. It's easy to use, just mix up two equal sized balls of part A and B and press over the object you want to mold.
Smooth-On makes good products and has some excellent customer service.
Here's their two part silicon putty: http://www.smooth-on.com/Silicone-Ru...133/index.html
Cut out some foamcore board to form walls around the gun, mix up some putty and fill up the box. Press the gun down halfway into the putty, and then press a pencil eraser into the putty a few inches away from the gun, to make key holes. Let it solidify and do not remove the gun. Seal the silicone with a mold release (Ease-Release, also available at Smooth On) and then do the same thing for the other side of the half of the gun, making a two part mold. The putty will go down in those little pencil eraser divots forming bumps that will lock the mold together later.
Once it's solidified, separate the two halves and remove the gun. Now you can use a resin, again available at Smooth On, to make a copy of your gun. You'll need to cut a pour spot, preferably in the spot on the mold where the back of the gun would be located to prevent air entrapment.
More than likely, it will cost more than buying one of those Bluegun safety training fake Glocks though.
Here are a few videos to show you how to make two part molds if my description is kind of lacking:
Two part mold video using liquid silicone: http://www.youtube.com/watch?v=b3eR89iGyio
I would not recommend using a pourable silicone because it could seep into the magazine well, or through the gap between the slide and the frame.