Like BBQ "low and slow" lol looks real good . I do walnut shell for 30 minutes if its nasty then cobb media for about an hour . if its fairly clean just the corn for about an hour always does it.
i used to be very anal about this by tumbling in walnut first and then switching to corn cob. it makes purty brass, but i just use walnut now with some dillon brass polish for about 12-16 hours. it works like a champ.