Try Birchwood Casey Case Cleaner. The solution is concentrated and goes a long way. I mix it with distilled water for the reason previously mentioned in this thread. The diluted solution needs to be heated. An cheap crock pot works well. This procedure will clean the outside, inside and primer pocket in a few minutes. If you want very shiny brass you can follow-up with tumbling in walnut shell with Iosso case polish for an hour or two.

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Doug