A lot of detail is captured in line-work, that can be translated into a digital painting by colouring the lines using a clipping mask.
I did this in procreate.
Here’s what I mean by translate.
Some lines can be translated to highlights, others can be translated into shadows. others still can be translated as the boundary between spaces, for example the bowndry between socks and legs or between fingers.
Additionally, the line-work layer can be used to hold some shapes like the hair or the eyes. Which can also be rendered in the same clipping mask.
It’s a quick way to work.
Here’s a 3 minute video of me colouring the lines.