No doubt my old school way will not get much agreement, but I can guarantee it will work (even with the cork gasket).
Clean off both surfaces thoroughly using scrapers (carefully) brass "toothbrushes" in curved sections and mineral spirits. Final clean the valve cover with brake cleaner. Make sure the valve cover isn't dimpled in around where the bolts were overtightened before. If so, use a ball peen hammer (flat side) and a block (or two hammers) to flatten it out around the bolt holes. Use gasket cement to glue the gasket to the valve cover. (Obviously, make sure the bolt holes are lined up good. You will have time to move it around while it dries.) Let it dry completely. Apply a thin coat of grease (wheel bearing or whatever) to the head side of the gasket/cover assembly.
This process insures that the gasket will not slip out during installation and replacement in the future will only require cleaning the valve cover on your bench instead of bending over the engine and scraping crap into the engine.
Then snug up all the bolts from the center out gradually. Using a 1/4" drive and first snugging up and then a final tightening down with one hand directly over the wrench socket with a firm twist of the wrist will be adequate. If you want to get fancy, don't let me stop you from using a torque wrench, but that is serious overkill. If you are not sure, use a torque wrench to get a feel for it.
Using this method, you will also be able to take the valve cover off easily and reuse the gasket without removing it from the valve cover.