I have been using ground walnut shells for years for cartridge case cleaning. With time it clogs up with lube & primer dust and will no longer work. On a day, with a light wind, I will go outside and pour it beteween two buckets to let the wind remove the dust. Next time I use it I add 1/4 ounce of paint thinner and it works like new again. Thought I'd pass this tip along to others that might find it helpful.