A few weeks ago I was commissioned to do a holiday card for an ADT employee. Here's how the magic happened:
This is a color study, which is just the pencil drawing with some Photoshop splattered on it.
Then, I outlined it (and gave a guard a sex change operation).
Here's a bit of the watercolour.
This is the final watercolour piece scanned.
This is the painting with a little bit of digital tweaking, cropped, and ready to go.