Make sure you spray in a well ventilated area. I usually wait for a sunny, reasonably warm, dry, wind-free day and do the spraying in the breezeway. Of course, I have to sweep it off first, but that doesn't take long. The quilt top does pick up a bit of surface "stuff" from the breezeway floor, but it shakes right off. I usually hold the spray can about 10 - 12" from the surface of the quilt top or back. Spraying closer than that layers it on too thickly and it is harder to work with.
NEVER spray near your sewing machine(s) or, for that matter, any machinery. The spray can move into the machinery - where you can't see it - and gum up the works.