Like Bananachipz said - Opticoat !!! research it. It's a permanent sealant like product that is professionally applied that is like a second clear coat. It won't come off even with multiple washes, etc. Only way to remove it is to polish it off. When it rains the water just beads off and it is much easier to keep it clean. Not cheap but you never have to wax again.
I'm picking our car tomorrow and it's getting an Opticoat treatment the following weekend.
2013 328i Sport Line, Mineral Grey, Black, sport auto,
2014 Carrera S, Agate grey, black int, 7spd manual
2015 BMW M235i, Estoril Blue, blk int, 6spd MT, m perf exhaust, m perf rear diffuser