[@BrokenPromise] Think of mouth cards exactly like your Chicken Run expressions. I've drawn a few mouth shapes for vowels, and I swap out the 'cards' on key frames to make it look like the character is talking, or looking a different direction. That's what I mean by mouth or eye cards. They're drawn eyes or mouths that I swap in between in order to match the voice acting.

Thanks for the tip, and I'm interested to read some of your writing. And let me know if you are interested in sharing some of your 3D or 2D art.