Just a WIP list of resources I find helpful for frame-by-frame animation, mostly geared towards hand-drawn VFX.
Fundamentals
Wave Motion: https://www.linkedin.com/learning/2d-animation-tips-and-tricks/tails-and-reversed-curves
Fire
http://flashfx.blogspot.com/2015/06/12-fire.html
References:
My Pinterest board: https://www.pinterest.com/jocarlostrada/vfx/
Awesome FX artists:
Alex Redfish: https://vimeo.com/user12223385
https://www.artstation.com/alexredfish
Michel Gagne: https://www.youtube.com/c/MichelGagne/featured
Jason Keyser: https://www.youtube.com/user/jasonkeyser
NaWakFX: https://vimeo.com/142720058?from=outro-embed
Rafles/Ruben: https://twitter.com/SrRafles/status/1102961346008760320