I use this wall method to spray my quilts, too. First, you tape newspaper to the walls around where you will be spraying (I use my design wall)- AND on the floor - to catch the overspray. Then you pin the backing to the wall wrong side out. Spray the entire backing. Pat and smooth the batting on. Spray the entire batting. Pat and smooth on the quilt top. Remove the quilt.
Now you can look at the back and check for puckers. If there are puckers, take the quilt to your cutting table and lift the bad areas and smooth them out. You can redo sprayed areas over and over until you get the entire sandwich exactly the way you want it. Chances are, if you carefull smoothed it out on the wall, you will have very little need to re-smooth after you take it off the wall.