So... for a bare wire connection at the back of the wall plate:

connect wire to wall plate
apply dialectric grease to the connection itself and to the end of the wire insulation
maybe use some heat shrink tubing as well over the top of the grease?

Sounds OK, but maybe a bit messy. The grease does not seem like a long term solution to me. If I have to go back there to apply more grease periodically, I might as well just trim the ends of the wire and reconnect. That is what I am trying to avoid here.

Any other options?