Hey Eileen,
This is a lot of work and money for a few small dings. Just like Pat, I would recommend just picking them out and using NO filler at all. A few hits with a body hammer and dollie and you could smooth them off with a sanding board or file. This is the way it should be done and it will be much easier then trying to learn leading and warping the whole panel with too much heat.
Practice on a scrap panel but this old steel is MUCH easier to work then the thin stuff they make today.
Just my opinion...
Mark