I'm curious on learning more about shrinking battings too!
However, please tell me how you did it in your top loader (which is what I have).
I did a small piece once, and just ended up with a mushy blob which I pulled apart ever so carefully, and once dry it appeared that there were sections where the batting had become so thin .. and other areas where it was thicker.
So please do share any tips for pre-washing via a top loader!
THANKS!!!!!!