This is taken directly from Todd Lassen's blog. It further explains how to take dents out of Expanded Shells. This was briefly summed up in my original post.
Here is the link to his blog: http://klansesklub.spaces.live.com/default.aspx
SO THIS IS HOW WE FIX SMALL DINGS IN COIN SHELLS
You can use any old wooden dowell. This one is about 1/2 inch diameter. This is just an old piece of nylon, wood works just as good or better. The end of the rod should be square or perpendicular to the rod diameter. If you just saw off the end of a wooden dowell, try to make it a nice straight cut. Now this end sits flush against the inside of the shell. Your thumb goes underneath, this way you can use your thumb to pry up on the rod while your fingers push downward against the shell. Now with my other hand, that you can't see (I had to take the pic:), I use my right hand to rotate the rod while applying pressure with the left hand. You can use a sorta rubbing back and forth action too while using the thumb to push against the afflicted area. Actually the smaller the diameter of the rod, the more focused the pressure can be in a certain area. But a little bit bigger diamter like this one will give you more of a smooth blended restore, this is just about the right size actually.
This method allows you to exert alot more pressure than you would imagine in a very focused area. If you can train your eye to see these little flat spots you should be able to fix up those embarassing dings in the privacy of your own home..and no one is the wiser. And using this non-invasive technique with wood will preserve the life of your battered shell ...far beyond life expectancies attainable by the highly skilled needlenose surgeons.