Wow - they gave a great response to your question/concern!
Although I am generally a member of the unwashed masses, I recently decided I'd best wash several yards of reds, dark blues and a couple of blacks that I am using in a current project. Normally, I use Best Press as I work (which I buy by the gallon when it is on sale, making it much less expensive than the 16 oz bottles most LQS have), but as I had so much pressing to do and had a can of Magic Sizing in the cupboard, I decided to give it a try. I found that it worked very well - iron glides over fabric, wrinkles are easily removed, and the fabric has nice body afterwards.
Guess it's a good thing I never did get to that project I originally bought the Magic Sizing for - an applique technique where you spray the sizing into a cup and use a small brush to fold edges back.