I take a gallon of salt brine water from my softener to the lake with me. Live minnows go into brine. Once home I lay them on paper and gently pat dry. Into a zip lock bag and add a cup of pickling salt. Shake them up a bit to cover with salt then into the inner part of an old salad spinner. Leave it in the outer bowl. into the fridge over nite. In morning back into the brine (which I strained with a nylon or cheese clothe) and gently swirl around to rinse off any excess salt. Lay on paper again and gently pad dry. Wrap a few dozen at a time in paper towel and store them in a ziplock in the freezer.
At no point do I rinse them off with clean water. They hold their scales well and are pliable and life like come summer. You can get a cheap salad spinner at the $ store.
Don't take too many as you're only allowed 10 dozen per licence.