as what others said dry when new spray with copper coat when reusing. One thing I want to mention is that if you are putting cometic style gaskets on an older engine the surface finish of the block and heads are critical to getting them to seal the best. Cometic gaskets are layers of stainless steel wich is very hard and durable, but they don't conform for any irregularities. The stock surface finish of all older muscle car engines is too rough.

file:///C:/Users/Hp280G/Downloads/FPTB-108-Surface-Finish.pdf