Portrait master studies

Here's a batch of sketches I mentioned I've done over the past few days. A did a whole lot more of sketching, but those are not for showing :P
Trying to get better at drawing faces by doing master studies.

Lotte study

Reference: "Lotte" by Carlos Schwabe.
TOZ color pencils in a Lega-lega sketchbook.

The Desperate Man study

Reference: "The Desperate Man (self-portrait)" by Gustave Courbet.
TOZ color pencils in a Moleskine sketchbook.
Done during a two-way bus ride to my parents' place. The greenish skintone was a hell to match, and of course I couldn't do it with the colors I have (I need some muted tones in my palette) and I'm generally very displeased with how I did this one.

Ink portrait sketches

References: "Portrait of Johannes Lutma" by Jacob Adriaensz Backer, "The Cellist (self-portrait)" by Gustave Courbet, "The Wounded Man" by Gustave Courbet, "Madame Barbe de Rimsky-Korsakov" by Franz Xaver Winterhalter.
Pentel brush pen in a Lega-lega sketchbook. Drawn straight with ink (no pencil sketch) so they're not very accurate. I was experimenting with shading in pure ink, I have no idea how to do it properly without stippling. More practice in order.

Will I post updates twice a day during the 30 day challenge? Should I even update the challenge every day or should I just do a batch post once a week or so? One of my friends hasn't even posted any of her drawings yet so I guess I shouldn't do that so often either.