BEFORE YOU IRON ON THAT SPRAY BASTING:
1) Be sure you are NOT using a polyester batting. It could melt!!!
2) Use a very light spray.
I use spray basting all the time, have for years. I have never one ironed it on. I also use cotton batting 99.9% of the time. In addition, I am a big proponent of hand basting. At least safety pin it.
I did a log cabin QAYG one time. I sewed each log by hand to the batting and batting. I did press each seam as I went (it was cotton batting).