For a camo I suppose you're looking for green, brown, black, tan?
I've tried a couple of berries and leafes as dyes, and while the fresh paint often looks great, it will quite quickly turn brown. In fact, most plant dyes that I tried turned brown within this year, even the green ones. Walnut is great, and it is already brown
From walnut, you can make a watery stain, that remains translucent.
Clay and coal is way better for covering paint. Also, ground iron compounds, comon rust as well, make good red. But you really have to grind away untill it is fine as dust. Don't sneeze. For the sticky stuff, I've tried linseed oil, egg, but I found curd is best, but it must be t low fat, else it won't dry.
For the green I think it will be difficult to find a good green stain.