[Brian]

Just normal grease Brian?

Yes David. You know how when you coat the sides of a gasket with [any] coating, and then when you torque the gasket down, all that 'goop' squeezes out around the outside of the joint? - yeah, well it also squeezes through to the inside of the joint too. If you use grease on the intake manifold gasket, any excess grease that squeezes into the engine is readily assimilated and does no damage. Other products, especially silicon rubber, I shudder to think about.
Grease will seal those minor imperfections, allow surfaces to 'slide' over each other as the torque is applied, and permit the gasket to easily be subsequently removed and indeed, even re-used!