Real brass-wire wheels are often used for cleaning steel things (like threads, tool parts, and such) while not taking off the base metal. They cost way more than steel wire wheels, and tend not to last as long. They would probably not work as well to grain aluminum plate as steel wire. A lot of wheels sold as brass are actually brass-plated steel wire, which would work fine - no harm for the brass to be there and might keep the wheel from rusting (as if that's a concern).
Ditto Doc's cautions about doing that outside, not only because of inhalation issues, but aluminum dust can be an explosion hazard. Though it seems unlikely for a small-scale job, it is still possible...as if you needed another reason to take it outside, I suppose.
