The brand of wool batting matters. What is the brand? If it's Hobbs or Quilter's Dream, you will be fine machine drying it.
The way wool batting is manufactured has changed radically over the years. Hobbs and QD both use techniques that limit shrinkage to a very acceptable amount. Not every brand uses the more modern manufacturing methods, so you do need to be more cautious with off-brands (and especially with homemade wool battings!).
Last edited by Prism99; 03-01-2014 at 12:04 PM.