Electrolysis works for me.
Caution: Don't do this if you have painted rims, or if you don't intend to clean and overhaul the hub too. Perform in a well ventilated area (hydrogen is produced in small quantities but can build up in a closed area), be careful as line voltage and water don't play well together (plug in you battery charger to a GFCI outlet).
Method: Remove tire, tube, rim strip and remove the axle and bearings. Fill a wading pool with water (or some container fits the wheel), add a half-cup of baking soda, baking powder, or washing soda (in order of effectiveness), toss in a sacrificial iron cathode (rebar, iron black pipe, etc). Connect the wheel to the NEGATIVE side of a 12 volt car battery charger and the cathode to the positive. There are many write-ups here and online about the setup.
Benefits: removes grease-dirt-rust, cheap, does not scratch, no harmful chemicals, does not hurt chrome rims or zinc galvanized spokes.