part of a batch of 500 38 specials I did a week or two back, no tumbler or pins used, just soaked in water, soap and lemon juice in a plastic tub for 2 hours and rinsed. 100 % clean on outside, 95% clean on inside, on the ones that had been deprimed maybe 50% clean on primer pockets. I can live without 100% clean primer pockets.
Next day I did over 2K 9mm's in one batch same results. Over the course of a week working 10 minutes here and 20 minutes there I cleaned enough 38's, 9mm's, 45 ACP, and 223 brass to last me for a long time, total cost less than two dollars
Only problem cases wil be the ones that are tarnished black and they will come out with a pinkish hue because citric acid won't remove the cuprous oxide which will be under the black copper oxide. You need to dry polish to remove that, or just check it for pitting and if there is none ignore it.