I just put together a little Automatic Kirby Krackle style that I’m pretty happy with. It could be better and maybe it will be by the time I’m done with the drawing I’m doing it for, but it’s more than good enough right now.
The top is the lines I drew, the bottom is what Illustrator turns it into when I use the following Appearance stack:
The magic here is in setting the “coruscation” scatter brush stroke to 0% opacity, and turning on Knockout Group for the whole path. This makes the brush’s clearness punch through everything applied to the path, instead of overlaying it on top of whatever other strokes and fills are applied below it.
And to give you a start on this, here’s the current brush settings. If I really wanted a serious Kirby Krackle I’d probably have two or three copies of the brush, one for big balls closer to the edge of the shape, one for smaller balls that go further in, and maybe one somewhere in between.
(Why has this been sitting in my drafts for a month and a half, this looks perfectly postable…)