TAZ,
Actually it doesn't have to be the booth or the area your'e spraying in that is the original home of the dust. Your filters and booth can be clean as glass, wheel wells clean, floor and walls dampened, and grounds galore if you want them but you can still have nibs. That is because most of them are created right there at the gun, or at least that is what I have read. As I recall from an article I read two or three years ago (sorry, no link) the problem of nibs (presuming all the usual care is taken to attain a clean work area) comes from the rapid drying of the "flash solvents" and some paint immediately as the material leaves the air cap. They are, as I understood the article, essentially just another form of overspray. Of course there are things that float around in the booth or make it past the filter(s); I'm not saying that its all caused by the gun, but the thing I read suggested that most nibs are. The problem was described as being much worse in dry climates or on dry days. As I recall the solutions suggested were the next slower reducer (yeah, just what you wanted to hear in cold weather) and to lower the air pressure into the gun by a pound or two (once again, as agreeable as stepping on nails barefoot). My solution is less elegant; 2000p and a Makita 9227c.
On Edit: Now that I'm thinking about it they may have said something about static electricity being caused by the turbulance of the paint leaving the cap or at the interface of the energized paint/air mix with the still air.
