Cleaning up safe plates

[Pschiffe]

I have a collection of safe plates in various conditions. The worst have been in a fire.
What is the best way to clean them up without damaging them?

There is a commercial product available on this side of the pond that I have been using for decades that works exceedingly well, Iosso Metal Polish:
https://iosso.com/clean/products/metal-polish/
We were buying it in 10 oz. cans but it looks like they now offer only a 3 oz. tube or 1 lb. or 5 lb. cans.

Pete Schifferli