I've been told by a couple of people with vast experience that the rubber gaskets are problematic. I have cast CB covers with the bales and NAPA sells a 6 pack of cork gaskets for $8.99. I can live with that I, too, smear them with grease before install, although I do it the old fashioned way. If nothing else, it keeps them in place while you put them on.
I don't know of the rubber gaskets would work better or worse on bolt-on covers