Not all fusibles are made for hand or machine stitching. Do you still have the package? You might have the type that is not recommended for stitching through.
What brand is it? Someone with experience using that particular brand may be able to give more detailed advice.
I found that the one-sided Steam-a-Seam worked best for me. It adhered well so I could skip stitching through it if I wanted to, I could machine stitch through it easily, and it did not make the applique too stiff. I did not like the more common two-sided Steam-a-Seam nearly as well; for me it made the applique much more stiff and it did not seem to stand up to washings as well.
Wonder Under gave me mixed results. I have read that Wonder Under gets old over time. It can be revived by re-hydrating (putting in a plastic bag with a damp towel for awhile). If it's old, it does not stick as well.
After testing hand applique on fusibles, I decided never to do it again. The only fusible I would consider hand sewing on would be the new Misty Fuse. I haven't had an opportunity to work with it yet, but the reviews for it are really good.