The brine formula is:
1 quart--Water
2 cups--Rock Salt
------------------------optional--------------------------
1/2 cup--Powdered Milk
2 tablespoons--Mrs. Stewarts Blueing and/or
2 tablespoons--Green or Blue food coloring
The soak time for herring brine is:
(1) fresh herring--overnight to 2-3 days;
(2) frozen herring--a) thaw them in the brine the day to be used, b) thaw them in a refrigerator the day before you use them, or c) near re-freeze them for later use (they won't completely re-freeze as there is too much salt in them, but they stay cold and usable later.
Note: The salt toughens the bait, the powdered milk sets the scales, and the blueing/food coloring adds the live color back into the bait.