I also got tired of case mouth peening and switched from wet tumbling with SS media to ultrasonic cleaning.
I use 2 tablespoons of dishwashing liquid and a 1/4 tablespoon of Lemi-Shine in my ultrasonic cleaner. This varies with water hardness and how dirty the brass.
The secret to ultrasonic cleaning is getting the water as hot as possible for the best cleaning.
I put hot tap water in the ultrasonic cleaner and run it for 4 eight minute cleaning cycles. And on the last cycle, the heater light goes out and the brass is good and clean.
Bottom line, the frequency of the ultrasonic cleaner, cleaning chemicals, and water temp affect the cleaning.
If you look at the MSDS of the ultrasonic cleaning solutions they contain citric acid and water softeners. So I use dishwashing soap and Lemi-Shine and save $$$.
Ultrasonic Cleaning 101
https://www.omegasonics.com/resources/ultrasonic-cleaning-101/?ppc_keyword=&gclid=EAIaIQobChMIiJvayYfg6gIVCQiICR3tAwCLEAAYASAAEgLALfD_BwE
I bought a Lyman clone on Amazon below.