I was sonic cleaning brass for a couple years and was really never impressed with it…tried just about every solution out there as well as homemade cleaners…but noting really gave me the level of cleaning I was looking for so I switched to wet tumbling and have never looked back.
I was in the same situation as you…unhappy with the results using a Hornady sonic cleaner to clean brass for a couple buddies as well as my own and it was a constant struggle to keep up (we were shooting a lot) and get good results. I looked at wet media stainless steel pins and ended building my own tumbler in the end to do the volume I wanted. Built a pretty good tumbler that is still going strong and I can take care of all our brass usually in one clean every couple of months (1500-2000pcs).
I can't say enough good things about wet tumbling…it is the best method that I have experimented with and I'm always shocked at how good it cleans brass…better then newly opened boxes of ammo! The stuff honestly looks like jewelry when you take it out.
You seem to be pretty picky like me so I can give good advice…Stop trying to find solutions to improve sonic cleaning, it can only get so good….it will never be close to perfect on any level.