For many years I've been using method which was recommended by the NRA in 1958. Soak in quart of vinegar and one tablespoon salt for about 20 minutes. Rinse very thoroughly in water. Tumble to polish if you want bright brass. Or use "as is". I'm now using a lot of range brass, for pistols and 223, some laying out for a good while and heavily tarnished. You'd think it was new brass when I'm done. Try a glassful of white vinegar with a shot of salt. Bet it will easily clean your brass.
