It's probably dangerous to describe how I processed this since it will show my ignorance, but what the heck: Images come out of the camera as regular RGB, and if they need adjusting I make them mono only (single layer), get the local and general contrast right, then flop them back to RGB for any toning that might look better. Unlike color images, the flop to single layer and then back to RGB has no effect at all on the resolution or other factors that's visible at 100 percent.
Edit: I purchased one b&w effects program and ran a dozen or more images through the 30 or so sample filters, and didn't like any of them. So I've stuck with manual editing only.