I've always used regular old Ronsonol lighter fluid. Put the bearings in a medicine bottle about half full with the lighter fluid...give them a good shake...let them soak...maybe shake a couple more times. Then I slip the bearing down on a sharpened pencil and spin it real good to get out the excess and then air dry them on a paper towel. One drop of Yellow Rocket Fuel and back in the reel. I have some old Curado reels that are going on 10 years old and still cast like new.
I'm not sure if its as good since I haven't used an ultrasonic cleaner, but I use lighter fluid in a small tupperware. Put the lid on top, and then turn on an electric razor and let it sit on the lid. Creates a nice vibration to the tupperware that cleans then pretty well to my standards.