Domestika - Introduction to Traditional Animation with Photoshop
http://www.domestika.org/en/courses/539-introduction-to-traditional-animation-with-photoshop
Learn the 12 principles of animation frame by frame and bring your stories to life
To get started in the world of traditional animation you just need a solid theoretical base and an experienced animator to explain everything to you in detail, like Rodrigo Miguel, better known as Numecaniq, whom you can meet for his work for brands such as Adobe, MTV, Spotify , Amazon or Adult Swim, or for its course 2D Animation with Photoshop: drawing, camera and action! in Domestika.