I mix up my own washes. There are plenty of recipes online, but video related has been the one I’ve used as a foundation for a while.

I somewhat follow the recipe in the description, though for my “nuln” I use 18 drops of black ink, and 8 of burnt umber. For the brown wash I use 16 drops of burnt umber, 6 of sienna, and 5 of black. I think it looks a bit better, but the great part with DIY is how much it can be changed up.

I keep steel mixing balls in the bottles and always give them a vigorous shake when everything is added.