I do them digitally too
AON gnawing on aquila, this will probably not get further than this unless i inspired

This is a kind of sketching I do that I call aggregative drawing; it's gestural and done in largely arbitrary colors, and they carry on until I have enough information to move to the next stage and/or I'm satisfied with how it looks. I do consider these finished work, of their own variety of artwork, as as prep work. Many drawings only ever exist in this stage.