I just stumbled upon a very nice illustration technique called, “Imitating A Scanner Darkly”. Be forewarned though—it’s not for amateurs! Unlike so many Photoshop and Illustrator techniques these days, this technique contains no filters or fancy plug-ins that do the creative work for you. You actually need to know how to draw to make this one work. So, artists and illustrators, step up! This is a fabulous effect and very well done. Kudos to author/illustrator Aaron Sacco.
If you really want a shortcut for this technique, you could use Photoshop to adjust the original photo in step one. Depending on the photograph, you could bring the image into Photoshop, create a Posterize adjustment layer, and then create a Black & White adjustment layer. Then fiddle around with the settings (or the stacking order) on both layers to get more simplified shapes in your photo. Then save the file and start with his step 1. Either way, you still need to draw all those shapes with the pen tool.
Digital tools certainly speed things up in many ways. But they cannot speed up the time it takes to draw something from scratch like this. No matter, it is well worth the time spent because the quality of the drawing is what makes or breaks the illustration, right?