A decent carnauba wax is the way to go mate - there are a multitude of fantastic products out there that include P21S, Soverean, PoorBoys Natty blue etc etc.
Actually with black cars I would recommend some for of Sealant such as CarLack68 Systematic Care/Klasse All In One (actually the same product) - this will give you an extremely high gloss finish. You would then apply (once you have buffed the CL68SC/AIO off to a high gloss shine) your favourite carnauba wax. The carnauba wax is what gives your car the depth of the shine and what some people call the 'wet look'. Basically you would apply the CL68SC/AIO as the base coat (it only needs to be done once) and then you layer the wax at the frequency you desire - say every 1-4 weeks. With regards to Carnauba Wax you can replace this if you prefer to have a more durable finish with say CarLack68 Long Life Sealant 'Acryl Wax' or Klasse Sealant Glaze (again the same product). Layering these products will build you up an extremely durable acrylic finish that is unparalleled for high gloss and depth of shine.
The reason you can not layer CL68SC/Klasse AIO is because of the cleaning agents in the product - they will remove all contaminants on the car including previous layers of wax/sealant. A lot of people who have decent paintwork are moving over from polishers to chemical cleaning sealants as they they minimise the risk of swirling due to no abrasive agents and are inherently better at removing and preventing oxidisation due to the chemical cleaning agents and the durable acrylic seal they place on the car.
If you have any further questions or would like to expand upon the above please do not hesitate to ask.
Mark
edited to add:
I would probably use CarLack68SC / Klasse AIO at a frequency of approx 3-6 months to strip all the old wax/sealant layers and any harsh contaminants that may have penetrated the protective coatings. At that point you build up your wax/sealant layers again.
