The Windex thing is true! It works way better than lotion. Cram a too-small ring on your finger and see for yourselfAnd it doesn't leave a film like soap/lotion, so if you have to use it to get your clean ring back on, it stays clean.
The partner-touch-it plan is a good one. I've used it for nasty watches ("Could you do this one? I tried and tried, but I just cannot get the back off of it."). It usually works for that. But when dealing with a finger locker, everyone else sees it happen too and they scatter like cockroaches to avoid a clever hand off.