Unless there's a lot of texture, hair or fur, for example, you should try to layer on your highlights. Dry brushing often looks unnatural and some figure guys will not even consider looking at a figure that looks dry brushed.
Now, as to lightening, it depends. Add blues to get a cooler black, good for a minimally used black leatgher coat. Add flesh for a warmer black, cloth or worn leather.
I just did some black hair on a bust I',m painting. I used Black gray for the base, added straight black over that, then did some mahogany (very dark) brown, dark and moderately dark brown, dark blue and finally just a hint of white on the highest layers to give the effect of a sheen.