here's the step, i hope it would be useful :)

1. i draw them with micron pen on A3 paper
2. scan, edit and coloring with photoshop
3. separate its layers ( leg, head, body )
4. move to after effects, animate them
5. back to photoshop reduce the size and convert to gif

the original size is much bigger around 20mb so i compressed them to 9mb but quality is not good as you can see here, it's grainy. but i don't want to waste people's bandwidth lol