Since no one has replied to this, I'll take that as a sign that no one has used the stuff.
Since my post, I've tried it out on a SIG P 220 that I bought used. It was a police trade in, so it had a lot of holster wear. I followed the instructions and applied the bluing. It worked very well, and it's a hard solid bluing. Actually an oxydizing. The color matches the original bluing perfectly.
I did make one mistake, in that I probably didn't clean the gun as well as I should have, and didn't keep it clean as I applied additional bluing. Consequently, I had a few spots that I didn't like, so I've gone after it with some 0000 steel wool, and I'm applying the bluing again.
I expect it to be perfect this time.
Has anyone tried any of the other cold bluing processes that I've seen offered in some of the gun stores?
Bob