I use mineral spirits in the big tank. When it gets to diluted and dirty, I put it in a separate tank that I use to pre-clean the really nasty dirty stuff to extend the life of the new, clean mineral spirits in the main tank. If performs well, no complaints. I use simple green and water in the ultrasonic cleaner. I always wear gloves before dipping my paws int any of this stuff.
Now, since mineral spirits has gotten so expensive, Sometime I pour a little bit of gas in a bucket and clean stuff outside.