I was given 100 rounds of surplus Yugo 8mm rifle ammo that had lots of green residue on the brass. I used Simple Green, full strength, which removed the green stuff. Then I wiped each round with a wet towel and dryed with tissue. The rounds fired fine in my Mauser.
As long as you wipe them dry after cleaning it might work.
Don't know about using Brasso, it might be a little too strong.
And if the ammo is pitted from corrosion or the residue is hardened it might be best to discard.
Just my opinion.