Dent Removal:

This works on fuel tank and other dents that don't involve a "crease" in the metal. Purchase a piece of dry ice (frozen c02) at your local liquor store. It should be larger than your dent. Using thick gloves or a towel to hold the ice, apply it to the dented area. Hold the ice in place until frost forms at least an inch beyond the dent all the way around. Remove the ice and place the tank or metal part in the Sun if possible. If the trick works you'll be able to watch the dent vanish before your eyes. This also works to remove many parking lot dents in car doors.
You can also use a heat gun to do the same thing as the sun I would just go slow.

Similar trick, but this one I've actually done.

My car got beat to hell by golf ball sized hail. I took the check from the insurance company and pocketed it. And went to work with cans of compressed air.

The same you'd use to blow dust out of a computer with. When you turn the cans upside down, out comes liquid CO2 (and some butane and other propellants). But it comes out darn cold and forms ice crystals.

First you want to heat up the area you want to work with, using a hair dryer perhaps or in my case: own a black car, live in the South and just wait till noon.

Hold the can of compressed air upside down, spray the dent, wait and listen. You'll hear the metal contract and pop the dent out.

May take a few applications to get the magic down, but my car doesn't look all that bad now. You really have to get down and look to find where the hail landed.