Pinning with safety pins is just one way of basting, it's the one I usually prefer. With smaller objects I sometimes sew the three layers together with big basting stitches. I've never used spray adhesive for basting and I never will. I'm not very fond of chemicals (you always breathe in some of it and even if you don't the production of it and the waste produced with the empty cans is bad for the environment) plus I wouldn't want the surrounding area to be all sticky.