Be careful drying with a blower as it is very easy to blow fine dust back on the car and then getting swirls and scratches. I use a blower but only for the gaps between panels, the main sections I dry with a drying towel. Also, dawn is very aggressive and tends to "dry" the paint: a good claying process (as mentioned in earlier answers) followed by a good All-In-One or a paint cleanser is the better way.
Current: ED 2010 535i, Carbon Black/Cream Beige&Black, 6sp, ZMP, ZPP, Nav, HUD, Heat, Shade, Folding seats
* beloved ED 2004 Mystic Blue 330i, 6sp, ZHP/Black Alcantara, Nav, Xe, brutally murdered by some dumb student who ran a stop while on the phone
* 2008 335i sedan, 6sp, Montego Blue, Terra leather, SP, CWP, CA, Nav