I use tooth paste and tooth brush to clean connectors, the rinse with water and blow dry. I then coat lightly with dielectric grease to prevent corrosion.

Quote

A connection may be coated with a lubricant in the case of moving contact to prevent it from seizing and welding. The conductive qualities of that compound would be unimportant, it could be either high or low as the compound's function is lubrication, not conduction. The connecting surfaces must have sufficient wiping action to actually clear the compound away from the actual conducting surfaces.


A stationary connection may be coated to prevent the contact surfaces' corrosion. The conductive properties would be immaterial to the primary function of the compound in this case as well.