Here is what Jim Lee tweeted,
"This is a very sped up clip of me messing around on my iPad. Original video was 20 mins in length; it usually takes me about 60-80 mins to get one of these pieces done using @sketchbookpro. I prefer using my finger to a stylus of any sort--makes it more fun. I honestly have to say this piece was not going in the direction I wanted so I stopped and got back to real work : ) but you get a general sense of how I layer on colors and work positive and negative shapes back and forth to get edges...like in painting."