urushi (Japanese lacquer) brush

thingiverse

Urushi lacquer is very sticky, so using regular brushes always leaves visible traces of the hairs. I found out that a solid foam brush works much better. Unfortunately, my local hardware store stopped selling them, so I got creative. You're going to need some sort of sponge to cut the tip from ("dirt erasers" seem promising, since they have very fine pores) and a rubber band to keep everything tight. Let me know how it works out for you. (The writing says urushi/うるし in Japanese, by the way.)