along with spreading smooth and spraying sometimes you also have to still baste (either with pins of with thread) at least the edges. if you are using a high loft batting that can cause it, you need to (lighten the pressure) adjust if possible the pressure your walking foot is putting on the quilt. spray basting does not always really hold well, the bigger the project the more it could move or pucker, for me i've only been successful with spray basting table runners/placemats, the quilts i wind up basting anyway so figure i am wasting the spray. some sprays hold better than others too.
you could try a tear away stablizer, that is what is used when you are embroidering to prevent puckering. then you would need to remove it when the quilting is done.