Here’s a character i refined with pencil and fineliner on detail paper. This was scanned (100dpi A4) and placed in Illustrator.
I used the pen tool to redraw it keeping all the various sections on separate layers. At this early stage i am just using greyscale fills mostly to get a sense of the values but also don’t want to be distracted by colour.
Here is the first colour version (above).
The vector artwork was opened up in Photoshop. I tried to give a more painterly look by using soft edged brushes.