The Animator's Survival Kit, by Richard Williams

Apparently this is a really good book that explains a lot of animation theory. Obviously it has the theory in it that you already master, but there might be something in there about clean-up and inbetweening.

+1 to this, it was my textbook for my very first animation class! You can find it on Genesis Library if you google for it ;)

We got it recommended in my animation bachelor. It wasn't mandatory, but I still bought it and read it. It's indeed easy to find a free PDF on Google. :D

aka the bible

cosigning this!

Hahaha that's a good name for it. xD

Drawing in betweens depends on the timing and what beats you want to hit with your animation as well as how smooth you want the flow of it. Normal fps is usually 24 drawings for that second. So if you take three points of reference, starting/middle/end for that set in a second you can then go from there by setting a path from start to middle by 12 drawings and the second half in another. You can break down even further for specific beats you want to hit.
Its easier if you have recorded a reference and have a timer to figure out what specific points of reference you must hit in that animation.

Plus im sure there are plenty of YouTube videos on this. I just wish I had YouTube before going to college and wasting a lot of money on AIA.

http://www.animationartist.com/colu....._tutorial.html

https://m.youtube.com/watch?v=sKHCl7yoQpE

The animator's survival kit is definitely a good call.

If you are talking just theory rather than a step by step guide, The Illusion of Life is an absolute must.

Both of them were my go-tos while at university.

About inbetweens, I think most of it has been said above, but I'm afraid cleaning up looks far simpler to most animators than the main animation work and thus nobody does a tutorial.
But I can say all you just need to do is draw clean vector lines (if you're working in Harmony, in OpenToonz, a Toonz Raster layer would suffice, since Toonz Vector is a bit weird to me, weirder than Flash/Animate) on a separate layer the same way you clean up your static artwork in SAI, but with onion skin enabled on clean-up layer to make inbetweens a bit less choppy than what Cuphead or many of the 90s cartoon shows got after their animation was inked (they probably inked each cel separately from the rest). And smoother.

Always buy the animators survival kit, It's literally the go to book for all animators. and the go back to book.

https://www.youtube.com/watch?v=86tqKH3zxuM
https://www.youtube.com/watch?v=0rp3zXBEhCE
https://www.youtube.com/watch?v=2bt8qFxEri0
Also second the emphasis on reading the Animator's Survival kit.

Fourth Emphasis on the Animator's Survival Kit. I regret I can't let you borrow mine. ^^;

Probably, this animation takes all the time

Sorry for the question. But why they decided to make a man / man?

Look up Aaron Blaise, he is veteran Disney animator and has animation tutorials on his site. He worked on Lion King, Pocahontas, ...Bambi I think, lots of the classivs