Yep, Walnut hull will work nicely (even though it stains)...and yep, we have the tincture of Black-Walnut hull (and soon the Apothecary will have *green* Black-Walnut hull and Black-Walnut bark).
I've read of & used castor oil for toenail fungus successfully...the only time it ever returns is when I'm not doing regular maintenance cleansing. I'm a serious barefooter (I only wear shoes outside, and only then when it's under 20-30 degrees)...so I've clearly seen the 'cause' is not a 'wet/damp environment' due to shoes.
Again & always, we've GOT to stop thinking through our conditioning (kill, poison, cut & burn to eliminate symptoms)! The cause of dis-ease is never a lack of pharmaceuticals, fractionated/isolated unnatural supplements or even herbs. The cause is a stagnant terrain (lack of flow throughout the body/organs) and lack of vital fuel/nutrition.
"Germs" don't cause disease anymore than mosquitos cause a pond to be stagnant! It's BECAUSE the pond is stagnant that the "germs" have the perfect terrain to feed, breed & multiply.
I know, I know, I'm preachin' to the choir...but there's no way we can repeat that truth often enough!