I've read Williams' book, and I've studied animation and done some, though I wouldn't call myself an animator yet.

I hope to avoid building rigs because they're, well, rigs. Much nicer and more flexible to control things though drawing than a rig which has a bunch of limitations and then there are issues with hair/cloth/water/etc. What can be done without a rig is another question but the methods I reviewed in this post are not the most that can be done for sure.