Sounds like where you do you painting is
dusty.
Just by using spray paint, you're stirring up the dust, which has to come down sometime. Unfortunately it's when the paint is drying!
I suggest vacuuming the area before painting. Maybe even putting the freshly painted body inside a box while it dries.
I've never done this myself, but I heard some guys put their cars inside food dehydrators to dry!
I've been saying this for ever but....
Put paint on in
SEVERAL LIGHT coats. Let dry between coats. Light coats dry faster so the dust has less time to collect!
Hope I could help!