Thank you all.
fabledgoat - I've often thought that Matt Dillon and Bruce Campbell looked like each other. They could easily play brothers:


Valence - What I meant was that it's easy enough (relatively speaking) to get a physical likeness of someone (it's just a technical excercise), but to really capture the person, you need to understand their personality, and get that across.
When drawing a caricature, I use multiple references, but there's usually one main one. Maybe I should do some kind of caricature workshop?
nickybeats - I was quite happy with how Matt came out, and he was fun to draw. I think I might do him again some day to a more finished stage.