I have a special attraction for ink and brushes. My favorite tools are the Pentel ColorBrush Pentel (red being my favorite) and the Pentel GFKP, I’ve been using them for almost 10 years now, and nothing beats their ability.
Most of the time, I raise the contrasts and lower the shadows with Photoshop, colorimetric corrections help to unify the shades.

I’m just beginning to use them for the preparatory sketches, it gives some cachet to the studies…

As far as portraits are concerned, I always erase the drawing and the constructions I did beforehand with pencil.