Art done in this style is usually not animated, since it's a lot of work to paint that stuff.
Photoshop has onion-skinning, but I suspect there are better animation-oriented programs out there that let you paint.
Another option is to paint->scale->pixelify just some key poses, and to create tweens by hand at the final size. With a sprite size like the example, it would be fairly doable, though still a pain to animate compared to a cleaner style.