This is a practice that I would do all the time when I was painting all-the-time, but couldn’t afford art-paper or canvas. it can be a challenge: since the paper is due to disintegrate under the paint and gives you a small area to work with. And it also has a lot of versatility due to both those things and more (such as the ability to play with the layers of the napkin.) Take this monochrome as an example: “this texture makes me uncomfortable in ways I do not understand”