Ed,
Anthony hit the nail on the head. With black paint especially the preparation is the key to a good result.
IMO the products that you use aren’t nearly as important and the techniques and methods - - especially with black paint! Pick an inconspicuous area and use it to practice. A 2 sq. foot area would be fine. Wash it with dish detergent , rinse, and clay that area. Dawn is a good detergent, and Blue Magic or Zaino’s clay are my favorites, but most brands are okay. Then try a polish by hand. You’ll learn whether or not you need to go to a power polisher. Do NOT use a rotary buffer, only an orbital! 3M Swirl Mark Remover is a good product here, but there are many others. Next try a finer polish or a glaze. Again, many products, most of them good. The last step is the paint protection and you have to choose between traditional carnauba which gives a deeper, more wet looking finish - or a polymer which gives more sparkle and a harder look. If you change your mind the carnauba can be removed with dish detergent and the polymer with rubbing alcohol
You don’t even have to do that whole sequence in one day. You can do a step or two and come back to it later.