Peening is the act of using an air pressurized machine to shoot a stream of tiny glass beads or large sand grains to take off something from a metal object. This is used a lot to remove paint from metal, as well as to "soften" the look of a shiny metal, or to get out some rough spots or get rid of rust on anything metal.
A lot of metal working shops have peening equipment. You might call around and see if any local metal working shops have peening equipment and see if they would peen a pan for you.
You can buy your own small peening machine, but its not cost efficient unless you are going to charge people to peen things.
As for the oil "stains" on the pan.......I boil water in the pans that get those. Whatever doesn't come off during the boiling is adhered to the metal.....it is ugly to look at, but you can still use it.
My granny said boiling white vinegar in a pan would get the gunk off the bottom, but I've never tried it.
Be warned, this will smell up your house if you do this!
