I use a pressure sensitive tablet (Wacom Bamboo Create) and it's all just brushing and smudging, man. First thing I did was do a simple trace/sketch of Foligno to know where all his features were. After that I layed down the base colors and from there it's shading. I watched a pretty good tutorial on how to do it and just kinda followed that.
https://www.youtube.com/watch?v=Iz7Nak-d5JE
It's pretty long, but he does a good job explaining and showing. He used Corel Painter for that, but it's the same gist of things. If you have any questions feel free to ask, I'll try to help.
If I have one piece of advice, it's to don't get discouraged if it doesn't look good at first. Until you really start getting in there with detail and all that shit, it's gonna look rough. I almost gave up early on.
I think what's lacking here is some much stronger shading.
Especially in the eye socket areas and around the edges of the face you'd get a much rounder, more realistic feeling with bolder shading and less of a flat picture. Same with the eyeballs themselves. You don't get the feeling that his eyeballs are actually round, but rather just a two dimensional thing pasted onto his face.
It's cool tho, just my two cents. I wanna try one too now.
Thanks for the feedback buzzo. Gonna take those points into consideration on my next piece.
And NoLa, basically what buzzy said. The pen/stylus just makes it a lot easier and gives you the feeling of actually drawing/painting. I know some people tape a piece of paper on top of their tablet to give them the feeling of drawing on paper.