Okay so as I'm drawing right now, I'm noticing something that makes lines feel more "natural" in my style. I'm using the airbrush at a really small size, like 3px. I'm treating those airbrush strokes like pencil lines, and 'shading' with them, making areas in shadow have a darker line. Before, I usually tried to paint over my hard-edged lines, which would result in a similar look (but a bit messier and chunkier because I've never been that thorough). So uhm, give the airbrush a try for reinforcing line work. I'll try to make a tutorial at some point that will address stuff like that!