Hi there, you can find a list of my materials here: http://blog.cliochiang.com/post/74197562671
As for locations, I draw people pretty much anywhere - cafes, parks, beaches, sidewalks, etc. I try to sit in a corner or far enough away that people don’t usually notice what I’m doing. It also helps if you’re not staring directly at them for a long time, as people can definitely feel eyes boring through their heads. It’s helpful to take a mental “snapshot” of the person and quickly get a gestural drawing of them down, and fill in the details as you see fit. Usually you can get a better caricature that way; relying on your memories for capturing the notable details, but not getting the exact likeness of them, ‘cause that’s what cameras are for. I use just enough time to take down what’s unique about the person (a facial feature, a pose, some strange piece of clothing, etc.), and fill in the rest out of my head.
Here is a messy messy process video. Basically a lot of layering.