Check the below link from the e90 forum. About half way through the post are detailed instructions on how to wash your car. When I got my 2007 335i, I found that thread.
Don't use quick detailer unless you just washed your car. You will end up dragging and dirt particles on your car across your paint marring your car.
http://www.e90post.com/forums/showthread.php?t=9145)