Sue Nickels taught us a technique. We use a double sided product and only use it on about the edge for 1/4 inch. Then we blanket stitch. She showed us a quilt that has been washed several times, gently, and there is no fraying.
Soft Fuse is the product and we use a blanket stitch that on my machine is 1.8 width and 2.0 length (bernina).