Good question! Photoshop itself is not at all required for After Effects, the only thing I would need is a drawing program that can save transparent images! And I'm sure there are lots of options for that! I divide up my drawings into sections like this

And this can be done in any drawing program! ^^ Not just photoshop ^^

Each of those chopped-up pieces gets its own layer, is put in its correct spots, then moved using after effects :D

Using whatever drawing program, you take your chopped pieces and import them into After effects

That little box up there, "Duik" Is something I seldom ever use, it is optional rigging! ^^ But if you look closely, you can see all my transparent layers! :D