Decap the brass, put it in a rotary tumbler and use stainless steel media. A little detergent and a little lemishine and run for two hours perhaps more if you have really nasty range brass. Looks brand new when done.
Dittos for me, I've one of those red 15lb tumblers with the stainless steel media and with the Lemon shine and a dash of dawn in hot water 4 hours will clean up the nastest brass and make it look brand new.