New Ultrasonic Cleaner

What solution would you use?
I think GeorgeJets has you covered but here's some more.

Cleaning Solution

ultrasonic cleaning fluid?

Any do's or don'ts?
Caution To Users Of Harbor Freight Ultrasonic Cleaner …

Something that might appeal to your electronics background is they are used to clean circuit boards and electronics with special solutions. I haven't tried that though
Yep! We had 55 gal drums of freon.
Under lock and key.
Every drop pumped out was measured and signed for. We only used small quantities but the (pre)production line used alot hence the quantity on hand.

from NASA
NASA Technical Reports Server (NTRS)
Ultrasonic cleaning: Fundamental theory and application

Bag technique
Technique for ultrasonic cleaning with volatile solvents eliminates need for hoods or condensers
NASA Technical Reports Server (NTRS)

https://ntrs.nasa.gov/api/citations/19950025362/downloads/19950025362.pdf?attachment=true