Usually I do my drawings on (small) paper with a pencil, but this has the significant downside of not being able to do anything with it.
But now, after more than a month (with a long stretch of downtime in the middle), I finally converted an old picture into a digital copy that I can proceed to do not much with. At least it looks nicer than a photo.
The process is quite simple: take an orthogonal photo with my phone since I don’t have easy access to a scanner, transfer it to my desktop, trace over all the lines, then continue switching between being overwhelmed and getting a little bit done anyway.
For instance, the scales took some time. I must say, shading with simple gradients makes a world of difference. Compare the version just before adding it (click for full size):