I have used Elmers glue for basting for several years and love it. At first I just drizzled in thin lines but once in a while would end up with a few stiff spots. I have found if I dilute it and spray it on, then take my hand and just smooth over the whole part that I have sprayed it distributes it evenly. After I have sprayed both sides I go over it with the iron lightly to just help dry it. It's the way to go for me!
Most of the time I do my spray basting on the bed. There's just enough give that it is so easy to get it smooth.