Place and smooth out your backing on the batting, then fold half of it back. Spray on the batting then smooth out your fabric back over it; doing the same thing again with the other half. Then turn over and do it with the top fabric. Just a light even spray is all you need....if you have wrinkles or bumps it is very easy to just pull back the fabric and smooth out again. 505 is great stuff...doesn't gunk up the needle and doesn't have a bad odor. If it is a good sized quilt, you should still do some pinning; but it doesn't have to be close like you would without the spray.
Good luck.