Some All-In-One cleaners have both cleaning and filling capabilities respond well to MB paints. Waxes and sealants are the LSP's (Last Step Protection) and that is what protects the paint and gives shine and gloss.
But as stated above, prep is the key to a good finish, especially for black. Everything from proper washing, to drying correctly, to using any polish to correct the finish, play a major role in how the car looks in the end when wax/sealant is applied. A good shine will either show off your great "smooth as glass surface", or highlight all of the defects and mistakes. To avoid the micro-marring and scratches that are amplified on a black finish, pay careful attention to the prep before you wax/seal. Also black is much more user-friendly to work with when cool and out of the sun.
MB paint is very hard and durable, but if you don't treat it right it can be a pain to restore and maintain. There are a number of good products that you can apply by hand for great results.
My MB has black paint and a good sealant such as Blackfire, or wax products like Meguiar's mentioned above are good choices, and there are tons more.
I have used Autoglym SRP and topped with Extra Gloss for a great cleaning, filling and protecting combo on my car, and am now using, and really liking, the Hydro Product line for black as well. Really fills well and is easy on/off. My neighbor loves his Klasse products for his black MB. Tons of great products to choose from, so shop around and try a few to see what works for you.
Sealants tend to offer better durability and protection but some people prefer the look of a good carnuba wax, so the choice is individual.