I live by a park that has lots of Black Walnut trees (I have one in my yard too, but this year it's being stingy with the walnuts) so I put on some rubber gloves, grabbed a plastic bag and gathered up some walnuts. There's a serious Black Walnut Fly problem here so any nuts that have fallen to the ground are rotten within a day from fly grubs so I tried finding ones that were freshly landed or just grabbed them off low branches. I dehusked them into an enamelware pot with some water in it, brought it up to a boil, and let it simmer for over an hour. Then I poured it into a cotton cloth to catch all the husk bits, wringing it out to get the most dye and put it into glass bottles. Grabbed a small piece of leather that I tooled and wiped several coats of the dye onto it, turned out pretty nice. The original leather color is below the bird. I like how the tooling captured more of the dye so the marks stand out.
Next time I'll try dehusking into a bag that I'll let sit in a bucket of water for a few days and try cooking that. I'll also try reducing some of the existing dye and maybe adding lampblack to it to see if I can get a nice ink.