Hi Nicolas,

Thank you for the kind words :) I have sent Jakub a photo of my drawing tools, but here's a quick rundown:

The background colors are from AD markers or Prismacolor markers. The blue is a Prismacolor Ceruelean Blue, the gray is AD Cool Gray #1

I studied Architecture long before I became an UX designer, so a lot of the techniques come from my rendering classes. I can recommend the book "Drawing and Designing with Confidence: A Step-by-Step Guide" by Mike Lin if you are interested in learning more about the styles.

http://www.amazon.com/Drawing-Designing-Confidenc...

Feel free to contact me through Twitter (b_rossi) if you have any questions -- I enjoy talking to others about design :)