I forgot to mention earlier, one of the greatest things I discovered for cleaning up and resurfacing most metals without removing any good material is a polycarbide abrasive wheel on an angle grinder it's literally a miracle worker, how you use it is you lay it down as flat as you can without touching the arbor to the metal and use light to no pressure on it because usually the weight of the grinder is enough.
You can use the edge of the wheel if you need to get into a recessed area.
It will remove, rust, body filler, paint, etc.
Here is a link to the product so you can check it out.
http://www.harborfreight.com/4-1-2-h...eel-94017.html