On April 6th, 2022, I was in a mental state comparable to smoking marijuana but which was more a mix of existential crisis, a little something I call "advanced not giving a shit," and discovering
Bug Powder Dust and immediately playing it on repeat. That's when I made a small lineart-only drawing program named shitart, inspired by the revelation that 1. drawing programs actually need a connect-the-dots algorithm in order to draw unbroken lines and 2. I can make this algorithm whatever in Samuel Hill I want. Ultimately, it ended up being more about applying filters that affect what the presumed start and endpoints are and drawing lines based on that. I made this screen for an unreleased level on April 13th using a filter that extends the distance of each line (and, of course, paint.net):

Being the post-apocalyptic wasteland raider I am, I'll probably snag this for Old Yeller.
(Note that you can get an even more natural "scribbly" style by also applying a filter that randomizes the position of the start and endpoint by up to two pixels away in each axis, but I hadn't come up with that filter at the time, and in practice it makes using the fill tool in other image editors way harder since that filter inevitably results in broken lines and spots where contagious fill can leak out.)