I have always used it as an anti-fungal

I've read that black walnut is also effective in treating a specific kind of alcoholism signified by frequent, small drinks which never quite result in drunkenness.

Topically for impetigo.

According to one of the websites which promotes black walnut tincture as a parasitide, the green hulls must be used. Ah! Found Hulda Clark's (whose books are the strongest promoters of Black Walnut Hull Tincture) recipe:

Black Walnut Hull Tincture from Cure For All Diseases

This new recipe is four times as strong as the previous one,
so it is called Black Walnut Hull Tincture Extra Strength.
Your largest enamel or ceramic (not stainless steel, not aluminum)cooking pot, preferably at least 10 quarts
Black walnuts, in the hull, each one still at least 50% green, enough to fill the pot to the top
Grain alcohol, about 50% strength, enough to cover the walnuts
½ tsp. vitamin C
Plastic wrap or cellophane
Glass jars or bottles
The black walnut tree produces large green balls in fall. The walnut is inside, but we will use the whole ball, uncracked, since the active ingredient is in the green outer hull.
Rinse the walnuts carefully, put them in the pot, and cover
with the alcohol. Sprinkle on half the vitamin C. Seal with plastic wrap and cover. Let sit for three days. Pour into glass jars or bottles, discarding walnuts, and divide the remaining vitamin C amongst the jars. If the glass jar has a metal lid, first put plastic
wrap over the top before screwing on the lid. Potency is strong
for several years if unopened, even if it darkens.
You have just made Extra Strength Black Walnut Hull
Tincture. It is stronger than the concentrate made with just a few black walnuts in a quart jar (my earlier recipe), because there are more walnuts per unit liquid. In addition, you will not dilute it before use (although when you take it, it will usually be in water).
When preparing the walnuts, rinse only with cold tap water.
You may need to use a brush on areas with dirt. If you are not
going to use all of them in this batch, you may freeze them in a
resealable plastic bag. Simply refrigerating them does not keep
them from turning black and useless. The pot of soaking walnuts
should not be refrigerated. Nor does the final tincture need any
refrigeration.
Exposure to air does cause the tincture to darken and lose
potency. To reduce air exposure, fill the pot as much as possible,without touching the plastic wrap, while still keeping a snugfitting lid. Even more importantly, the glass jars or bottles you use to store your tincture should have as little air space as possible, without touching the plastic wrap on top. A large jar should be divided into smaller ones when you are ready to use it.The idea is not to have partial jars, with a lot of air space, sittingfor longer than a month or so.
There are several ways to make a 50% grain alcohol solution.
Some states have Everclear,TM 95% alcohol. Mix this half
and half with water. Other states have Everclear that is 76.5%
alcohol. Mix this three parts Everclear to one part water. Yet
another method is to buy vodka that is 100 proof. This is already
50% alcohol.
Remember, never use any kind of purchased water to make
tincture.
Black Walnut Hull Tincture (Regular Strength)
This is the potency I used originally. It is included here in
case you prefer it or wish to treat a pet. The Extra Strength recipe is four times as potent as the original recipe, so it must be diluted in quarters. (Similarly, if you have a lot of the Regular Strength left and want to use it in place of Extra Strength, simply take four times as much.)
Black Walnut Hull Tincture Extra Strength
Grain Alcohol, about 10%
Mix one part extra strength tincture with three parts of the
10% alcohol. Store in glass containers same as described above.
There are several ways to make a 10% grain alcohol solution.
Some states have Everclear,TM 95% alcohol. Mix this one
part Everclear to nine parts water. Other states have Everclear
that is 76.5% alcohol. Mix this one part Everclear to seven parts
water.
Yet another method is to buy vodka that is 100 proof
(50% alcohol) and mix one part vodka with four parts water.
Black Walnut Hull Extract (Water Based)
Because you do not know how commercially available extracts
were made, and may not be able to test for solvent pollution,
it is wisest to make it yourself!
This recipe is intended for alcoholic persons: cover the
green balls in the 10 quart (non-metal) pot with cold tap water.
Heat to boiling, covered. Turn off heat. When cool, add vitamin
C, cover with plastic wrap, and the lid. Let stand for 1 day. It
will be darker than the tincture. Do not dilute. Pour into freezable containers. Refrigerate what you will use in two days and freeze the rest. Add vitamin C after thawing or during refrigeration (¼ tsp. per quart).
For use: in programs calling for Extra Strength Black Walnut
Hull Tincture use four times as much of this water based recipe
(8 tsp. instead of 2 tsp. Extra Strength).
Important Note: do not use bottled or purchased water to
make this tincture or you could pollute it with benzene!