Paint and Body GT front bumper cover alignment

After having gone through this same type of issue several months back (though with a new bumper cover), I can add only a little here. Wayne hit most of it in his reply. DEFINITELY start at the top. What I can add is to loosen the radiator support to fender brace on one end and totally disconnect the other end. You can still access it from under the car once the bumper cover is in place. Follow Wayne's suggestions and when done THEN reconnect and tighten down the support brace. I'd also suggest a helper to hold the cover in alignment while you tighten the retaining nuts. The support brace tip was given to me by the owner of the late model Mustang salvage yard where I bought a few parts and it proved to be very helpful. Good luck!