Cleaning old brake dust off trim rings?

Picked up a full factory set of original Rallye wheels for my 66 Valiant yesterday and are in great shape. The only issue is 2 of the trim rings seem to have in-bedded brake dust that the PO never cleaned. I can take my finger and feel the small deposits all over the trim ring. I tried soap and water, but it didn't work. What's the best way to get this off? Or should I just purchase new rings? These are the chrome plated factory trim rings.
Thank you....