I just saw another thread that, I don't remember what to call them, pens were used. I used these in a past life as a graphic artist. I only used ink but a video show them being used with paint. I have a bunch of Testers enamel paints I'm going to try.
I was able to find mine. They need cleaning but I think they'll work.
https://www.bikeforums.net/classic-v...ing-brush.html