I have been working on a technique with decent results. First I wash the blade with soap and water using a plastic pot scrubber. This is to partially degrease and partially to remove any easily removed rust. Then I degrease with Windex following with a vinegar soak. This gives similar results to the product you are using. After that there is still some patina, the rust is almost entirely gone, and pattern welding shows with high carbon steel darker than the softer parts. The problem is the graying you have mentioned. So I polish the blade with 6000 grit micromesh (
http://micro-surface.com/index.php?main_page=page&id=15). The micromesh gently brightens the gray areas without completely obscuring the pattern brought out by the acid.
Josh