In making this it was helpful to have a timer on so would get down a few key poses. (for the 2d sketching i used a 10 minute timer, the facial expression and 3d sculpt was about 2 days )
It was helpful using the 3d sculpt as a reference for sketching.
It was helpful making the 3d sculpted face have some personality (like nonsymmetric expression etc)
It was helpful taking a couple minutes before drawing to think about what kind of fun things the character does.
It was helpful keeping original concepts in a single folder with an image for each one so can quickly go back to iterate on an idea.