Ahh, I understand the question now....
If I use Lightroom (most cases) then I use the Black & White button in the develop module. I can then use the swatch to change the tone of individual portions of the image.
If I use photoshop (occassionaly) then I use the black and white adjustment layer with similar swatch as in lightroom, and with curves and levels.
Unfortunately I'm lazy (impatient), so I tend to use the most convenient method at hand
Phil