I wonder if I can get my reply posted before someone tells you to do a search for this, then shove it. Autobody filler is the way to go, but not bondo. I forget the brand name, but the can is yellow and it's a two part product. There is a blue tube of hardener under the clear lid.
The stuff in the can is like a dark mustard color. When you've mixed in enough hardener, the shade of green is medium. When mixed that way it's very workable four about 5 to 8 minutes. It bonds seamlessly, sands to shape easily, takes paint primered or not, and can be built up with additional coats if worked down too far. With this description you can find this product at Auto Zone or maybe Sherwin Williams. Post pics man!