[springerpete]

You really have only 2 choices as you know. For my 29 I washed the plates well with soap and water, used a little liquid car polish on a wet cloth ( for dilution ) and buffed with an old towel. Then, I sprayed them with a clear semi-gloss enamel from a rattle can. They look old and have a nice preservative coat that does add a bit of lustre.