Speedpainting walkthrough

I have to admit that i have a mixed feeling about speedpainting, it almost like drinking coffee to fall asleep. In one hand we have the stress factor of "speed", in the other the calming (soothing) activity of "painting".
Jokes aside, it's a neat one layer work. Closest thing to traditional painting that digital can provide. I love the initial sketch, the girl has some very piercing/inquisitive look.
May i ask in what resolution (size) do you usually work a piece such as this?. And what tablet?
Cheers