I have used Nanolex Professional on my last two new 911's and can recommend it, it is a sealant using the latest nano technology, basically it forms a protective layer on top of the paint so dirt is easy to shift, especially brake dust. My current car is Basalt so I have to work a little harder on insect removal, but my last was Aqua and it was fantastic. It is supposed to last for two years if you treat it properly, but you need to have some idea of what you're doing when applying. Have a nosey on detailing world, really helpful forum with loads of advice and contacts (including recommended detailers).