I deprime the brass first and then put 50% white vinegar and 50% hot water in a beaker with a squirt of dish detergent. Soak the brass in the beaker and then put the beaker in ultrosonic cleaner for about 10min. Rinse the brass with water and add some baking soda in the beaker to neutralize the acid and rinse the brass again. Dry the brass with compressed air or just put them under the sun. The brass came out clean and shining.
BTW, If you do not have an ultrosonic cleaner, just soak the brass in the mixture of white vinegar and hot water for 15~20min and then rinse them. It also works pretty good.