I soak and rinse and squeeze my batting in HOT water keeping it still folded. when it is semi dry I put it in a pillow case and roll up and squeeze again then dry it on medium heat. Most batting has a 3 to 5/6inch % shrinkage. to me that is a lot. all my supplies are washed. after all my work I do hate surprizes...
with old batting pop a fabric softener in there. good luck
:idea: if the smell does not go away, use it for pet bedding with some cedar chips in it. I use old pillowcases for my pups filled with scraps/old reused batting with cedar chips . just have to sew up 1 seam.