meanmom, I haven't tried pre-soaking wool batting because the potential shrinkage indicated is very small. If I recall, the wool battings indicate shrinkage of 1-2% while the cottons say 5%. I guess the wool shrinks quite a bit when it's being processed for the batting.
The method I've used for Warm & Natural is given on their label. You soak the batting, squeeze it out, press between towels and put in the dryer on warm. Some people have said that they spin it (but the package says not to, so I haven't).
The only other batting I've pre-soaked is the Hobbs silk. The above method didn't work well for that; it absorbs an enormous amount of water and is quite stretchy when wet. So I handled with extreme care and laid it out to dry the last time, and that worked well.
I remember reading an account by someone who had tried pre-soaking Hobbs Tuscany wool, and it dissolved! Quilter's Dream wool is thermally bonded, and I was told that if exposed to heat, it will completely flatten out. Quilter's Dream urges that their batting not be pre-soaked, as it is so easy to damage when wet and heavy (although the rep who responded to my email did concede that it would be okay to pre-soak a cotton bat and lay it out to dry, if done very carefully). I will probably do that with Quilter's Dream cotton; I can't wait to try that, as everyone raves about it.
I think if you pre-wash your fabrics, wash your quilts before passing them on, and include washing instructions with the quilts when you give them away, you shouldn't have to worry too much about them.