Thanks for sharing that. I find the smudge tool works too.Don’t rightly know. It wasn’t a straightforward process, but some sketching and doodling that turned into something. Some airbrush, some niko rull, a lot of different pencil strokes layered on top of each other. Like hatching, cross hatching, drawing with the side of the pencil etc.
You can try my pencil brushes if you like. They’re old and may need some tweaking to suit you.
https://procreate.art/discussions/10/28/22413?page=1