Polishing champleve enamel.... but metal only

Hi,

I like kiln polish as last step for enamel but I would need to do something for metal (copper) parts that are visible on top. My dream would be sand paper that would not mark enamel but would grain metal but that probably don’t exist. But if there any tool/abrasive that would work like this? 3M rotary wheels…etc?

Thanks!