If there is interest in this sort of thing I will go back and detail it at a later date. However, I will be including more like this plus code, scripts, makefiles, etc in my "making of the game" book.
I didn't see any code, but it sounds like the post was detailing how he marks (manually) which section of his models will have a dither pattern -- basically just masking.
There are a a bunch of posts about it if you go to his blog index, there are only 7 pages so it's easy enough to flip through them, they're all labeled with the DailyDriver name. There might be something in there about the render process.
It’s the upcoming Playdate, developed by Panic: https://play.date/
For browsing my blog you can also click on the tags at the top of each post, which will show you other posts with the same tag. For my game that's: https://blog.gingerbeardman.com/tag/dailydriver/