One of the classes on Craftsy shows ironing after spray basting. I can't remember the class or the instructor (mental block!). She seemed to think that the ironing set the spray basting. However, she did mention ironing very lightly and carefully.

I never iron when I spray baste. I use 505 and it works well for me every time. Not sure if it makes a difference, but I use clamps on a large table surface when spray basting. I could never crawl around on a floor -- knees and back are too bad!

My thighs are sore today from all the kneeling, squatting and crawling I did yesterday. I was thinking it would probably be good for me if I basted a quilt every day!