What lubricant is suitable for switch contact?
The defining feature of dielectric grease is that is is a good insulator, and is used to keep moisture away from contacts where it could cause corrosion or conduction. Any silicone compound will break down under arcs leaving a silicon oxide that is an even better insulator, pretty much guaranteeing damage to the contacts.

Switches should be greased with a high melting point, high viscosity grease on the pivots and sliding mechanisms only - where it will hopefully not migrate to the contacts, which should be dry.