Best Grease Dielectric? For Firewall Connectors

I think the stuff "anti ox" you buy at the electrical supply stores would work fine, and Lowes/ HD probably have it.

First time I saw grease in connectors, was in the 70's selling "Trucklite" sealed truck tail lights and then when I bought that old 78 Ford LTD II the connectors used a white looking grease. If you can find out what Ferd used......