For 30+ years I've been using crushed walnut hulls, treated with jewlers rouge in my case tumbler. For cases that I don't tumble, I use a gizmo (technical term) that I bought from Sinclairs. It has a spud that goes into a drill, this piece is male threaded and has a centering button that goes into the primer pocket. The other piece has a slot specific to case rim diameter size and screws down together to hold the cases against the centering button. The cases are spun, cleaned and polished with ( I use 4-0 steel wool or gray Scotch Brite). It cleans all but the grungiest cases to look as good as or better than new, but is very time consuming as you can only do one at a time.
those who beat their guns into plowshares, will plow for those who didn't