Check out Quilt Roadies video on youtube.
https://www.youtube.com/watch?v=HPkAnMwvRHE
She gives a lot of good info on prepping your wool applique. There is also a Wool Applique group on facebook.
I use Heat n bond lite or Fine fuse. I've had no problems stitching through either one. Some people staple the pieces-I found mine still shifted with that method. Glue sticks just don't work on wool. Good luck & happy stitching!