WARNING!!!!!! I have only begun to experiment with this and although it looks promising it still may need to stand the test of time!
A friend of mine was showing me a Marlin 336 he had blued and it looked great! He explained that he had cold blued it first (I forgot to ask the brand but it was a simple cold blue from a bottle, not the higher tech Brownells stuff) then followed that up by heating it with a heat gun and doing three cycles of the Mark Lee Express Rust Blue process. Even in bright light this thing is stunning with no trace of streaking or light spots and it seems to be as tough as normal rust bluing, he rubbed it vigorously with steel wool without changing the hue in the least. This was after only three cycles of the Express Blue process but he told me that even the first application looked nearly as good as the finished project, I am not sure I would want to do an entire gun using this method but it might just be a real trick for doing small parts.
So far I have only experimented on one part, a hammer for a cheap single shot shotgun, I polished to 320 grit then heated the hammer with a heat gun and applied the cold blue. I followed this immediately by re-heating and one application of ML's Express Blue then boiled in distilled water, ONE cycle and the darn thing looks finished! I have a very fine wire wheel from Brownells made just for rust bluing and using this I buffed the dickens out of that thing and all it did was polish it. I followed up with 0000 steel wool and rubbed it to the point I am sure cold blue would have been completely removed but it still looks good after all this.
I don't have a clue why this seems to work like it does and I may be "jumping the gun" because it may be too soon to say for sure but this looks really promising (for small parts anyway)!