Much of it is based on Aaron Blaise's technique. I recommend his tutorials. He's a very skilled artist who has developed an effective process, as opposed to me who is trying to be a better amateur. I use Krita rather than Photoshop because I prefer it. The core process doesn't change.
I had doodled an idea in pencil that I scanned in. Then I refined the pencil using a pencil, well a digital one 'Pencil Large 4B' in Krita. From various attempts I'm leaning toward an ink brush, for this picture I used the pencil for texture. Not sure it mattered. Having good line work really does matter to me. I'm a lot faster without having to 'find' the image as you do without lines.
Under the drawing layer is one for flat 'local colour' aka the 'Flats' in the comic world.