I've posted this before; it's from an old NRA reprint.
Mix one pint water, 1 cup white vinegar, 1 tablespoon salt, and 1 teaspoon of detergent (laundry will do). You can mix it in a mayo jar or any quart jar will do. Once combined, dump in your brass and shake off and on for about 10 minutes. Guaranteed to clean up brass really well. Once done, drain liquid off so you can use it again. Rinse the brass off. The brass can then be dried in the sun on a towel or you can put it in a mild oven for a few minutes. I use the sun method. Once dry, decap so you can make sure the primer pockets are free of liquid.