I was glad to see and old topic on cold bluing back up. AzRedneck hits on something that I found works "heat". It doesn't seem to mater where it comes from a, torch, hair dryer, or hot water. I have been using boiling water. Clean and drop the parts in boiling water. Let cool and dry a couple minutes then apply the cold blue. Then back in boiling water to remove the cold blue solution. Let cool down awhile and steel wool. Repeat until you get the uniform color you want. I get a very good looking finish this way. I use Casey's Super Blue or Perma Blue.
Now that you spent hours filing, sanding and buffing, why not rust blue your baby. If you do all your metal prep, you can get a cheap deal on Hot Bluing.
A few pics of a Turk I am working on. It was in bad shape as seem in the bolt shroud. The projects goal is to improve my metal working skills. At times I wanted to go the J.B. weld and spray can route. The receiver was sanded to 400 grit and cold blued.