Both FACs or 2 ADRs are probably the fastest and safest way to put the aircraft in alternate law. From what my chief pilot told me, in the good old days, to be instructor in my company it was mandatory to do one approach in direct law in the real aircraft and they were switching both FACs to force the aircraft to go in alternate law . Until 2 years ago, it was mandatory during the base flight to do one single engine approach, SE go around, followed by single engine landing.