Heating Panels for larger dents assists in allowing larger dents to come out a little easier.

However, in applying the heating process, it is important to use sufficient to heat the panel that if touch by hand it is sufficient to be uncomfortably hot for the hand to touch. This means that the metal can be heated but the paint will not be damaged. Too much heating on the paint as can be seen int he demonstration picture  (for demonstration purposes of course) near the hand can burn paint.

In heating the panel, wave the touch at a very slight angle left and right over the region of the panel you are trying to make a little more flexible to push. When it is sufficiently hot as suggested above, you will find pushing the metal easier in the case of what would have been a difficult and large dent!