Go have a look at the animation bootcamp 2023 https://cgcookie.com/courses/animation-bootcamp
good stuff there!
Take a look at PANELS for more Grease Pencil learning, It is an awesome course to learn to use layers in Grease Pencil, essential I guess to animating with Grease Pencil.
Panels is a comic book creation course, however learning Grease Pencil with still images first will set you up for an easier time when moving on to animating.
create-rigged-grease-pencil-animations-in-blender is an option to learn grease pencil animation, however it is a little old.
An updated Grease Pencil Animation course is probably over due. Perhaps Paul or Wayne may look into it soon, or even both could collaborate on a course.
Thanks for the suggestion, Assim! 2D animation and 3D animation share many of the same principles. Is it more Grease Pencil-specific information you are after? Thankyou Adrian - I'll check that course out and see if I can put it on my schedule to update! Sounds really promising!