Just get black rtv, pull off the old gasket, clean it with a simple green soaked towel/old microfiber, then use your fingers to coat the whole gasket in a thin even layer, set it in the cover with the cover upside down, seat it in place good, give it 5-10 minutes so it sticks to the vc, then put it on, lightly snug it down, give it another 10-15, then torque it down.
I've done it twice on the geezer, once on both valve covers on the stang, and three times on the F4. Haven't had a leak yet. :lol:
As long as the gasket isn't damaged or crusty there's no reason it shouldn't work as long as you do your part right, and it's easy as fuck.