I suggest you log onto the Brownells web site and download their instruction booklet for their Dicropan IM product. It is what is termed an "Express" type of rust blue, and the procedure is much what you describe. I have used it for 8 to 10 years with great success and really like it. You would be quite surprised at the number of newly manufactured guns coming in from Europe now that use an Express rust blue. It gives a deep black finish which you can vary by your prep method just as in any rust blue method. My "go to" upland gun is a 1933 Merkel side by side 16 gauge that I finished with Dicropan perhaps 7 years ago now, and it gets a lot of use. The finish has held up very well, and I continue to use it when I refinish other shotguns. At any rate, get their free booklet, it'll answer your questions.
