when using spray I do it on the floor- first putting down a large old sheet to catch any overspray. then I smooth the batting down- spray it, place the backing over the sprayed batting, smooth it all out evenly starting in the center and working my way out to the edges- when I have it all smoothed together well I pick it up, flip it over, spray the other side of the batting, smooth the top over it...then I let it dry for a little bit- make sure all is secure & pick it up to go to the sewing machine. *all that being said- I don't spray baste really large projects- generally just table toppers/runners, tree skirts, small items- so, I don't know if my method will work as well for a large project; in my mind it would be the same*