Clean them or not?
For years and years I wiped my brass with an old chunk of cloth and did fine, or so I thought.
Rattle tubs filled with various grits do an excellent job. Dust, noise, sometimes residue build up and are the down side. The outsides look great, the insides, not so much.
Simple soaps or detergents with water takes off oils and surface gunk, but doesn't clean off the discolorations. But, hay, they are clean.
Rock tumblers with steel pins and all sorts of fluids work quite well. Of all of the thousands of rounds of brass that I have cleaned with steel pins, I have found maybe half a dozen cases with two pins wedged in the flash hole. Cases are clean inside and out, primer pockets included.
Sonics or ultra sonic cleaners. I have a little one, aren't they all little? Unless you spend copious amounts on them? I tried it, it worked well, it too too long to process with the small size and limited number of cases I could do at one time. With a larger (much larger) tank, this would be a good option. For now I use mine to super clean AR bolts and BCGs.
That's about all I can think of at this time.
Things to avoid are any fluids that have detrimental effects on the brass.
What do I use? I rattle tub first, size and deprime, rock tumble with steel pins, then load and wipe em down with a cloth. Humm, maybe I get carried away some times.