I can't think of any videos that show thinning behind the edge. My suggestion would be to get one of those really wide Magic Markers and paint the blade face at least halfway up toward the spine so you can see where you're removing metal. Then work at a shallower angle than you sharpen and see where you're grinding. When thinning, you don't want to be hitting the edge at all. On a gyuto, look to thin from between 1/2" to 3/4" up from the edge, blending the grind into the blade face by reducing the angle as you go up. As with sharpening, use progressively finer grits to remove the scratches from the coarser ones.
I've only reprofiled a couple of blades. I did it on one knife to repair a really large chip, but on the other I flattened out what I considered to be too much "belly" in the blade. It is a PITA to do by hand because of the large amount of metal to be removed. The first step is to shape the new profile of the blade. Mark out where you want to remove metal and then "breadknife" the edge on a coarse diamond plate or waterstone to the new profile - take the knife, place it on the plate or stone, edge straight down, and try to cut the plate or stone like you would a loaf of bread. After you get the new profile established, use the techniques for thinning the blade to establish the geometry you want. It will need a lot of thinning, and you will probably have to grind higher on the blade face.
Rick
Can be dowloaded on his website.
