Kryton, I had my M3 detailed by a guy who comes to your house and does a fantastic job . He put me onto a Maguiars product that I use all the time now. It's the detail spray, use it to get rid of water spots and little fingerprints etc. i also have a proper duster from a detailing package I bought .
There are a couple of detail sprays but I use the one in the black bottle (most expensive) . I also have one called "Final Inspection" by Maguiars, it's a bit less so I only use it on the Gf's 325Ci but it's pretty good too. I'll check the website and get back to you....
(I think it's almost the same as the spray you get with a Clay kit..)
Edit: It's called "Ultimate Quick Detailer" by Maguiars