The Parkerizing process does not fill the pits, but rather changes the surface to a sandpaper-like finish which is good for the adherence of oil (or the spray-and-bake finish) to the metal. I hand sanded down the pitting and tried to contour the barrel and other parts as well as I could. The parkerizing does "soften" the appearance, but it doesn't fix the pitting.
The link that you provided is not it. That looks like "Bondo" which is an automotive body filler. I have seen a gun pit filler product made by, I think Lauer which makes the Dura-Coat product, but I have not used their products.
-Chuck
http://www.brownells.com/aspx/NS/sto...%20PARKERIZING