I started reloading pre-web so I didn't know what I "needed" to get good shootable ammo and just wiped my brass with a solvent dampened rag. When I did start tumbling, I used walnut media with nuttin' else, got excellent results. When I saw reloaders wanting a high polished, virgin looking brass, I experimented with a bunch of stuff. Nu Finish, "Scratch Away", most any auto polish, flake carnauba wax, and mineral spirits all work to some degree, but I settled on an old jug of Turtle wax polish. I don't need high gloss (ain't nobody to impress!) and just like a light coating of wax to help prevent tarnish on stored brass. I don't want/need glossy brass except for my Garand and 1911 brass, where shiny is easier to find in the dirt, rocks, etc. of the "range" where I shoot, but the wax left on the cases allow long term storage without tarnish...
I'd just add some more mineral spirits and shake it up...