Who hasn't forgotten that they left the brass tumbler running for longer than they intended? This outlet timer has a one time countdown function that would be perfect for plugging a brass tumbler into or perhaps a food dehydrator/brass drier.
https://www.walmart.com/ip/Generic-WC2021-Indoor-Daily-Digital-Timer/46683950
https://www.walmart.com/ip/Generic-WC2021-Indoor-Daily-Digital-Timer/46683950