Personally I haven't had that much luck with powdered milk but some do use it in herring brines...

My most popular herring brine is done with a dozen at a time.

First, I cover the bottom of a 8" x 14" tupperware bowl with rock salt then I fill it to 3/4 full with water. Then I cut plug my herring (take guts out of herring) and throw it all back into the herring brine including the head and guts. I add a cap full of anise extract and a about a teaspoon of Liquid Joy and on occassion a capful of blue liquid dye depending on water color I'm fishing.

All in all it's pretty basic but one of the best formulas I've came up with.

Keith