If it is small enough, I'd suggest picking up some MarineTex epoxy filler and then fill it and refinish the surface. Of course, this option requires painting. If the dent has stress cracks, it may be tough getting it too look nice if you try other methods. But, it you just want to level it out, you can try your method or try a small puller kit from an auto store.
If you are planning on repainting as part of a restoration, I would just recommend the filler route.