I use that sizing also. But I spray and then let it sit a few minutes to be absorbed into the fabric fibers. Then I press.
I try to put sizing on fabric right out of the dryer and as I cut and piece. So far the Magic Sizing $1 from Walmart has worked great.
I've heard that starch is made from organic products.
http://www.generations-quilt-pattern...lt-fabric.html
Here is a good explanation.