bondo?

[hotroddr]

how small are these dents you speak of? If they are less than 1/8" (which they should be since you need to work the metal as smooth as possible) I would use a product called metal glaze. Its a greenish blue 2 part glazing putty NOT TO BE CONFUSED with one part spot putty in the tube. Under no circumstances should you fill holes with any sort of body filler, weld them shut then fill them. If you dont moisture will get in from behind and your repair will rust/crack.
The other benefit of metal glaze or 2 part glazing putty is that you can apply it over paint primer or body filler as long as you rough it up a little. Hope this helps you, see my suburban link in my sig for all kinds of bodywork pictures.