[TowerTalk] Cleaner

[Gene WØQFC]

I hope that this is not too far off subject.
I have a ultrasonic cleaner that I use for cleaning small parts in the shack and garage.
I have head so many different stories about what cleaning solution to use and I have tried a lot of them, usually with poor results.
My question is: 
Are there specific solutions that could (should) be used for, like pot metal, brass, stainless steel, etc.?
I have talked to some of the on-line companies that sell cleaners and they always want to sell me something or other that sells for $60 a gallon!
Any thoughts out there....?

Gene, WØQFC