Hi I used a Sonus black wax on my car, it is coloured black so protect your hands, but it leaves a brilliant Gloss, very easy to use with repeat operations every couple of months, I then use quick detailer during the intervening periods!!! Sonus is also used by Mercedes Mcclaren, But as Yorgi said with black you need to have a good base to start with, so clay bar with Menzerna and a detailing machine will give that base then it is a matter of upkeep!!
I also have used a carnuba wax (do it correctlyand it is very easy to apply and builds a depth of gloss) but it is affected by really hot climates.....
Always said I would go back to a 6 series