The nice thing about when a hardcover slipcased edition of a book like GAHAN WILSON: FIFTY YEARS OF PLAYBOY CARTOONS is published, is that there are some good interviews with Mr. Wilson, who has been cartooning for something like 50 years.
Via The Stranger's Paul Constant, here's his process for a full page cartoon:
"The Playboy [illustrations] can go on for quite a stretch, because I do really elaborate production with those. Because it's color and full page, it's a series of sort of underpaintings. I'll do the pen drawing, then I'll do the first color, then I'll spray it with a workable fixative, and then I'll do another color on top, or some other medium, sometimes. Sometimes I'll do more watercolor, sometimes something else. With New Yorker [cartoons], sometimes I'll do the thing to the point where I think that's all I can do, and then I'll set it down, and then just sort of sneak a look at it as I pass by, and then the next day, check it out again, just to see, and stuff will pop into view that I had missed. So that's how it works. It's not regular. Sometimes it'll take a couple of days, sometimes it'll take a little longer."
Hat tip to Journalista!