Took a couple hours last night to sketch and paint this out on the iPad.
Here's a character study for a project I'm about to start, two of the main characters--art below and video showing progress below that. The video shows how I color and shade in the Brushes app on the iPad. I usually use Sketchbook Pro to do the rough sketch, bring it into Brushes to refine, color, shade, outline. I usually finish up in Sketchbook Pro--also using some filtering tools to adjust overall lighting, tinting, contrast.
To finish up, I brought the image into the Filterstorm app, dropped the contrast way down, and darkened it up, also brought the warmth and sat up.