I love Best Press for the fabulous scents - I would buy Caribbean Beach and Cherry Blossom in perfume form, if I could! :)
But I've found that I prefer liquid starch mixed 50/50 with water in a spray bottle for preparing fabric prior to cutting it.
I soak the fabric, let it almost dry, then steam press it to dry all the way.
When you spray unwashed new all-cotton fabric with any liquid, it's going to curl up and shrink to one extent or another. Some of them seem to hardly shrink at all while others look like Shrinky Dinks plastic in the oven!
What surprised me the most is the difference in shrinkage between the lengthwise and crosswise grain - some of my fabrics have shrunk twice as much along the crosswise as with the lengthwise. What could distortion like that do to your cut and sewn quilt block? :shock:
That's one of the reasons I starch beforehand - to get that shrinkage done before I cut and sew. (and, lazy me, so I don't have to pre-wash! :) )