Apply gloss black is meant for Alcad paints and has little to no effect with MM Metalizers. MM Aluminum Plate should be buffed an hour after it has dried, and no sealer has been applied. Make sure to buff in circular motion using a clean cotton cloth. MM Aluminum (Buffing) is another option, but won't come out as shiny as aluminum plate.
What are you using the Gloss Aluminum for? I don't know of any part that would stay shiny very long that would be made out of aluminum. If you really want a shiny aluminum then I suggest you use SnJ Aluminum, but it is a difficult and very expensive process. Alcad Polished Aluminum is another way, but $7 a 1oz bottle.