The "Magic Balls" just look like copper ball bearings. I think the rice idea is best. The brown much is likely stuff that seeped into the randy during the aging process and prolly can't hurt you much. Put in some rice, swish around with cool water (too warm and the rice might cook!), rinse well, then follow with a good rinse of boiling water. I'd advise against citric acid, it could react with the metal on the inside of the flask