I LOVE Hobbs 80/20 fusible quilt batt. You do need a large surface to dry iron the sandwich together. I use the old carpet on my basement floor. I have done up to a twin size quilt without a wrinkle in the back.
I recently tried the 505 spray and hung a small lap quilt in the garage to make my sandwich. It did not make as nice a quilting sandwich as the Hobbs fusible, but it still worked without any wrinkles in the back. NOTE: I used the 505 with a puffy polyester batt so that may have made the difference.