Is there a way to completely deflate an inner tube? I had a flat tire and replaced the inner tube. I just didn't realize that the tube was a thorn-proof tube when I bought it. It was the only spare one I had, so I used it anyway. Just now I replaced it with a regular tube. I figure I can keep this thorn proof one around just in case I get another flat. 

The problem is, I can't get all the air out of the thorn proof tube to store it in the closet. It's schrader valve. I push the pin in and air comes out, but there is still a lot in there. I'm trying to fold it up like a tube of toothpaste while pushing the pin, and it's not working so well. I could cut it and patch it, but then I may as well throw it out and buy a new tube. Is there maybe some way to get my bike pump to work in reverse or otherwise completely deflate this thing?
According to Yehuda Moon (google it), you can take a properly-sized ball bearing (or even a pebble) and put it inside the valve cap, then screw the cap halfway so that the ball/pebble will keep the valve open.

Then, you roll the tube like toothpaste, and when you finish you remove the cap and the pebble to avoid the natural elasticity of the tube to suck back some air.

Hope this helps