I have never prewashed batting.
If I were to try to get the wrinkles out I would spray it with water, then put it in the dryer for a while. I wouldn't want to handle the batting once it had been in a tub of water.
Someone on the board posted a picture of a quilt she has used wool batting in.......there was so much shrinkage she ended up taking the quilting out and redoing it....so you probably do need to prewash wool batting.