Been trying out several line and colour combinations on Procreate. Digital pen lines still aren't convincing enough. Real ink using a fountain pen or dip pen still work best for me. But I do like these digital watercolours (AquaReal watercolours by Lisa Glanz). Looks real enough. Good for painting over lines done with ink that would bleed if it interacted with water.
And yeah, I used sumi black ink for this. It works even on this paper that would bleed through if I used regular inks.