well there are brush pens that have water reservoirs in the handle you can add ink and dilute it with a cap it stays wet and you can mix values ahead of time
https://www.amazon.com/Pentel-Frh-b-Aquash-Water-Brush/dp/B0017OLHN2/ref=sr\_1\_34?crid=ZWUQ0NTIL1HX&keywords=brush+pens+water+handles&qid=1659148483&sprefix=brush+pens+water+handles%2Caps%2C140&sr=8-34