I've ironed my quilts without issue. W&N is all cotton. I also saw something in a Craftsy class where the teacher said when she opens up a package of W&N or W&W batting, she unfolds it & lets it sit on a tabletop/counter/floor for at least 24 hours and then the fold line creases all come out. Maybe if you just lay it out flat the creases will work themselves out.
I try not to line dry my quilts. If I do, I rotate them every hour (vertical to horizontal) to help them dry more evenly, prevent creases, and keep it from getting pulled out of shape. I'm going to BB&B Friday to purchase a drying rack so I can dry my quilts flat.
