[gdnyc]

From what I have seen, Zaino works the best and looks the best. It lasts about 6-9 mos depending on the weather conditions. Initial application can be tedious, but subsequent coats are very easy and increases the shine and reflectivity of the paint.
I used Zaino on my old Brilliant Black (jet Black equivalent) Audi A4. It looked great. I haven't Zaino'ed the BMW yet, but I will in about a month or so.
Before applying Zaino for the 1st time, wash the car with Dawn dish washing soap. Supposedly this will remove a good portion of the wax and oils that are on the paint.
If you add coats of Zaino after the initial application, you will extend the life of it. Depending on how you wash your car and other factors, if you do get swirl marks, then you will have to polish it and start all over.
I don't think Zaino and carnauba waxes mix very well. You will not need to top Zaino with a carnauba.
Klasse is a great polish and sealant to work with as well, but on darker colored cars it doesn't give such a great shine as Zaino does.