Filling dents w/solder?

If you aim to do a job that requires heat application anyway, you should try shrinking the dents as much as possible first. You would have much less filling to do. I've heard of people letting the car set out in the sun on a hot day then putting dry ice chips on the dents to shrink the metal. It works too. It won't cost mutch to try it.

The torch & water soaked rag works well too. You would be surpized at how much dent is left after this process. On shallow dents, there is almost no visible sign. Most could be filled with prime & sand or a skim coat of the dreaded bondo.