If you're talking about a creased body line, keep in mind that a dent ON the line warps the entire area above and below......gentle body hammering is necessary, and best with a "dolly" or other flat piece of steel behind it.....very slight flattening can be done with an 80 grit disc.
When you have the areas flat, check them with a straight edge (very important....you MUST have consistency.....a hair LOW is OK...a hair HIGH is not). Use thin layers of filler, and a hand sanding block that is longer than the repair area.....a 6" repair should be flattened with at least a 12" block...if not, you run the risk of "waves" in your work.
Always sculpt using a perfect area as your reference..if you screw it up, do it again........the actual line is the most difficult......when you have a good shape completed, and have NOT cut the body line too far, try shaping it with 100 grit or higher paper to keep from over-cutting.......very delicate shaping...patience, a straightedge, and perseverance. :read2:
