Dielectric Grease - nope
Picky comment, but you want to avoid "dielectric" grease. The term "dielectric" implies that it is a very poor conductor (like the dielectric in a capacitor, which insulates the two terminals from each other, or the insulator between the center conductor and the shield in a piece of coax).
A good metal-bearing grease formulated specifically for this purpose is available, called "Butter It's Not". It's a molybdenum grease with copper particles in it. If the surfaces aren't aluminum, this will work well. If they ARE aluminum, there's a product called "Noalox" (grease with aluminum particles).
If you stick an ohmmeter's leads into either of these greases, you'll see an open circuit, but what happens is the particles "bite" into the metallic surfaces and that's where they provide protection and conductivity. Just remember to remove all the paint, rust and dirt from ALL surfaces to be joined.
On edit: I see I got bit by the kopperhead kops :roll: