Here is the finished piece of President Obama. I wanted to include an in-progress example for those art geeks like me who might be interested.
In my process of creating the finished illustration, I started the picture like a traditional watercolor painting. I stopped the painting process at about mid-point, where finer details and values would be applied with paint, and instead used India ink. With the ink I used a nibbed pen, brush, and stippling techniques. No trade secrets here, just good ol' fashioned drawing and painting.