[Mike621]

"Step 1
Check your local yellow pages for a dry ice dealer in your area. Take a Styrofoam chest to carry the dry ice in. Do not touch dry ice with your bare hands.

Step 2
Put on gloves. Place a chuck of dry ice on one or more of the hail dings and use a towel to help hold the dry ice in place. Make sure the dry ice is in direct contact with the metal of the car. You want the dry ice to freeze the metal. Leave the dry ice in contact with the metal of the car for a full two minutes.

Step 3
Remove the dry ice (return it to your Styrofoam container) and immediately blow hot air from a hairdryer onto the frozen metal with the hail ding. The sudden change in temperature should cause the metal to expand and "pop" out, making the damaged area look as good as new.

Step 4
Rub the area gently with 0000-grit steel wool if there are any tiny cracks in the paint around the dinged area. Wipe the area with a damp cloth and allow it to dry.
"

I have not used this technique personally, so I cannot recommend it from experience.