Actually my first comment was misleading. I meant to say wash with water in which baking soda has been dissolved to neutralize the acid.
As EOD said, acid shouldn't be used. If it changes the appearance of the case, it degrades the original look and value. There are some collectors that want to see the tool marks on a projectile from the final turning. Of course everyone likes original paint, and that's why there is so much discussion on the forum regarding what to use to remove the rust and corrosion but not harm the paint, so sandblasting the outside to remove rust, also removes the tool marks and the paint, which is akin to heresy to some . Some people get a buffing wheel and polish brass cases to a mirror finish. Yeah, it's shiny, but it isn't in the natural state in which it would have been issued and used. It looks shiny, but it isn't realistic. Of course it is yours to do with as you wish.
The Romans said it all: "De gustibus non est disputandum" or "In matters of taste, there can be no disputes"