I've used the B/C Brassblack on brass sights (hate em!), and I wasn't too pleased with the results. Even on that small a surface it came out pretty mottly, and way too thin in places. I'm curious if with the right solvent (water, even?) you couldn't thin the product enough to make a larger volume of "wash" and soak the parts longer. Food for thought.
In any case, I have to retreat the sights pretty often because it wears off so easy on the sharp edges. I suspect that if you were using it on larger parts, especially the butt plate, it would be showing brass real quick unless you covered it with something hard. Maybe even a spray-on epoxy gee whillicker kinda hard finish that you could subsequently dull with steelwool. Sorry to say that kinda thinking may be in order here. Not for T/C, I'm looking for more ideas, but may ultimately have to sort out the steel question.
Let's hear more bout using bluing solution to blacken brass!!!! Never heard of it, but I'm real interested.