Someone emailed, asking what I do to get them looking so good.
I simply use a wet sponge with one of those green scrbby backs, to remove the dirt and grime and use the green side on nasty stains to take the edge off. After it dries, I use "Mothers Metal Polish" and an attachment for an electric drill thats called a "Mothers Power Ball". Its a bunch of small foam pieces in the shape of a ball, that has a shaft attached to it. This shaft will attach to any electric drill and has a hard plastic sleeve over it, that allows downward pressure from your free hand!
This Mothers Metal polish has no abrasives in it and will not scratch the surface like abrasives will and really polish's it to a high shine. It won't remove scratches but it gets the dirt out of the scratches so they are fairly invisible.Aftr application, you simply wipe off with a clean dry rag until the excess material is wiped clean.
When used on porcelain that has lost the gloss finish, it will do a good job cleaning but will NOT restore the lustre.
Its great stuff and it takes some work to do a complete sign, but the results are worth it.