Be careful with liquid additives ... too much , it loads up and clogs the walnut shell media . Don't use it every time you tumble ...only when the media stops / slows down .
Media will not last forever no matter what you add to it ... it becomes clogged and the surfaces load up ... time to change it .
Use the treated shell media from Midway , Lyman's is too wet , it has way too much liquid additive from the start ... adding more just makes it worse . and doesn't last as long as Midway's brand .
I use Rooster Lab's Bright Brass Cartridge Polishing Additive , it's made for walnut shells , sold by Midway too .
I would also give Turtle Wax Chrome Polish and Rust Remover a try ... it seems to be a similar product but just formulated for chrome ( I use it to clean firearms and metal parts of light surface rust)
Regardless ... use either sparingly !
Gary