I posted this many years ago, seems like it was on this forum. A MUCH younger forum.

You need:
1. Orbital hand held sander
2. Coffee can. Metal if your cleaner is mineral based, plastic if "green".
3. Wire clothes hanger, cut and straightened with a hook on it (to hang the wet chain)

Take off your chain, into the coffee can it goes.
Add cleaner of choice. PUT THE LID ON THE CAN, it will splatter.
Flip the sander on to it's back and HOLD the can on the pad.
Turn on the sander for however long you want.
Repeat as necessary.
Remove the chain and use the clothes hanger to suspend the chain to dry.