Inspired by Barry and other artists, Kleon has developed his own notebook practice over the years. This guy is a really dedicated notebooker! He keeps THREE notebooks going at the same time (a logbook, a diary, and a commonplace diary). Here are his posts about his notebook practice.
In Syllabus, Barry recommends pasting/taping stuff into your notebook. She expects students to fill up 3 to 4 composition books over the course of a semester. Kleon similarly puts in lots and lots of stuff, from notes taken when listening to podcasts, to collages, notes to self, cartoons, doodles, & scribbles.
Here’s a more-or-less random example he’s posted online:
I notebooked from about 13 to 37, stopped from 37 to 53, and have been notebooking the last few years (~5ish). I don’t think I’ve ever completed the equivalent of 4 notebooks in a semester. (One a month?) I also wasn’t doodling, drawing, sketching, and scribbling so I’ll see if I can pick up the pace this cartoon sprummer.