There is probably a Guzzi-specific instruction on this, but I use bare gasket where I want it to stick. Perma-Tex gray or similar would be good there, if any surface irregularities exist. On the opposite surface, I use a very thin layer of synthetic grease on the gasket (i.e. valve cover gasket to head) in cases where it will be removed. If you bond both sides of a gasket, you will almost certainly have to go back in for some as-yet-unknown reason, usually Murphy's law.