here we go again... Nothing personal Ken!
I always run a cork gasket that has been hi-tacked, RTV'd, or some other fuel/oil resistant sealer to the valve cover and then just clean the head.
I could never get the rubber one to seal, even after RTV'ing both sides and letting it dry for two days, leaked like a sive.
And using my method for the cork you can also reuse it, the one on my 68 has been on and off at least a dozen times and still no leaks