Annoying dent in my rear door, thought I'd give the hot and cold method a go.
Basic principle is to heat the metal up, until it's hot to touch so it expands, then rapidly cool it using compressed air to contract it again.
Note: using a heat gun or blow torch would most likely result in a loss of paint! Use the wife's hairdryer... Or pretend it's the wife's of it's actually yours..
It's not going to get every sent out but isn't bad.
Mine looked like this to start with:
After some heat and cooling using these:
The result is this:
It's not perfect and still has a slight crease, which would always of needed professional work to remove. However it's not as bad by a long way and very cheap!