I'm with GingerK, press, not iron. I used Hobbs heirloom 80/20 fusible for years. Does not make the quilt hard. Washes well.
I started using pool noodles to roll my quilt top or back out of the way and then spray baste, roll toward me and spray and so on. I have two folding tables i use to put the quilt on for this. I'd never get up off the floor!
now i use good spray basting. I bought a bad one and it sprayed all over my floor. too wide of a spray. I tossed that one! spray going across the quilt and back and down. like using hair spray. Not too much in one place.