I love 505...Spray it on both layers, either on the batting or the fabric. It doesn't take a heavy application. I usually layer everything together, then fold back about half the batting and backing layers. Spray the back of the quilt top lightly. Carefully pull batting back over it and spray the batting. Now pull the backing over the sprayed batting and smooth. Then do the same with the other half. When you are through smooth all the layers. You can lift and reposition without a problem. Be sure to have all the surfaces around the quilt covered to catch any over spray. Turn off ceiling fans or any thing that will blow the spray around. :D