OK, I've heard back from my nephew. He agrees that the badge's surfaces need to be cleaned and prepared for a successful plating.
It might be more than you are looking for, but here is how he would approach things:
1. Submerse the badge in lacquer thinner (not mineral oils) and let soak to remove remnants of coating materials. The soak duration to be determined by how long it takes to see remnants begin to bubble and loosen.
2. Clean with soapy water. Dry.
3. Use a Dremel-type tool with wire brush to remove any remaining remnants.
4. Wet sand wirh fine grit metal sandpaper (NOT sandpaper used on wood!!!) A grit of at least 1000 is recommended - finer would also be OK. Sand only in straight lines - DO NOT use swirling mtion. (Available at most auto parts stores.)
5. Clean with soapy water. Let dry thoroughly.
6. Plate as planned.
I've seen some of his work - he does a nice job!
Good luck! Let us know how you decide to proceed / how things turn out!
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