I don't think of myself as an illustrator. I think of myself as a cartoonist. I write the story with pictures - I don't illustrate the story with the pictures.
Unlike prose writing, the strange process of writing with pictures encourages associations and recollections to accumulate literally in front of your eyes; people, places, and events appear out of nowhere. Doors open into rooms remembered from childhood, faces form into dead relatives, and distant loves appear, almost magically, on the page- all deceptively manageable, visceral, the combinations sometimes even revelatory.
Comics is different than writing because when you draw something you are trying to visualize it and you are trying to put yourself in that space. And when you're drawing something, all sorts of associations come up in my mind that I never would have thought of otherwise.
The real power of comics is writing as you draw.
Storytelling is one of comics' esthetic hurdles at the moment, which was the novelist's problem 150 years ago: namely, to take comics from storytelling into that of "writing," the major distinction between the two to me being that the former gives one the facts, but the latter tries to recreate the sensation and complexities of life within the fluidity of consciousness and experience. As far as I'm concerned, that's really all I've been trying to do formally for the past decade or more with comics, and it's certainly time-consuming, since it has to be done with drawings, not words.
As I get older I find myself thinking about stories more and more before I work so that by the time I eventually sit down to write them, I know more or less how it's going to look, start or feel. Once I do actually set pencil to paper, though, everything changes and I end up erasing, redrawing and rewriting more than I keep. Once a picture is on the page I think of about ten things that never would have occurred to me otherwise. Then when I think of the strip at other odd times during the day, it's a completely different thing than it was before I started.
I arrived at my way of "working" as a way of visually approximating what I feel the tone of fiction to be in prose versus the tone one might use to write biography; I would never do a biographical story using the deliberately synthetic way of cartooning I use to write fiction. I try to use the rules of typography to govern the way that I "draw," which keeps me at a sensible distance from the story as well as being a visual analog to the way we remember and conceptualize the world.
Fortunately, I'm able to make a living from comics, so I'm privileged enough to be quite choosy, though most cartoonists can't afford to be. It's really an uncomfortable situation, since I'm not an illustrator, though I do get calls from morally indefensible businesses offering me money to decorate their ambitions. It's extremely rare, almost unheard of, in fact, that I am asked to do a comic strip. Do writers get calls to pen Toyota advertisements? Do composers get asked to write chamber pieces about exercise machines?
I do worry that beginning cartoonists could feel somewhat strangled by the increasing critical seriousness comics has received of late and feel, like younger writers, that they have to have something to "say" before they set pen to paper. Many cartoonists feel even more passionate about this idea than I do, vehemently insisting that comics are inherently "non-art" and poop humor or whatever it is they think it is, but that attitude is a little like insisting that all modern writing should always take the form of The Canterbury Tales.