Janet,
You asked about using fusible on batting. I recently had a bad experience with some some batting. It was an expensive wool batting, scoured, super-washed, machine washable and advertised as thermally bonded so you could quilt up to 8" apart.
I tried to get the wrinkles out by steaming it lightly, with the steam iron on a wool setting, several inches above the batting. It flattened into a fused, thin tortilla in some places. I tried everything I could think of to fluff it back up, but nothing worked. It was useless.
This surprised me, because I had learned in my tailoring courses how to steam wool. I checked the packaging. It was bonded with polyester. It had to be the heat melting the polyester bonding into the thin layer of wool fibers.
So, learn from my mistake and be careful using heat on batting with a fusible anything that melts.