I love fusible applique, and have made many quilts with it. I like Steam a Seam Lite fusible. I don't have too much trouble with fraying, but as was mentioned, careful handling and proper pressing is vital. Could you be using a fabric that freys alot anyway? I also use 2 strands of embroidery floss to blanket-stitch them after fusing and make small-ish stitches. Also, it is important to handle carefully your pieces while appliqueing and just before I stitch a section, I cut any wayward threads there may be. Don't think there is much else you can do. As long as it is fused well around the edges, a little fraying shouldn't be noticable.