I don't agree with your service guy. I have spray basted quilts for several years and had no issues with my machines. Just spray lightly---not heavy or soak the fabric. I also let it dry overnight before starting to quilt on a sprayed sandwich. Like you, I didn't get good results with pinning--always got tucks. Never had a tuck since switching. Sorry I can't help on the glue method--never tried it. But many here swear by it--most say they dilute the Washable school glue with water 50/50, then either dribble or brush the glue on lightly. Would be cheaper, but seems to me like it would potentially be more gummy than spray.