Walnut ink is messy, at least in the container I have. India ink is a better option. It’s cheaper too. Working with one color helped me focus on the feel of the brush and how to work with the medium. I focused on the shapes of the flowers instead of mixing the right hues.
I was working with a big brush and it holds a lot of water. It would be interesting to try inks with cotton paper. On my cheap paper, the paint went all over the place, making it hard to add darker areas.
BUT I don’t usually work with walnut ink. It felt good to try a new tool. Have you painted with inks? Coffee? I will probably use the rest of this ink to paint trees. A bear? Perhaps I should make a list of all things brown? Start a collection?