If you can't/don't want to blanket/straight stitch each piece of fusible, then you need to make sure that you quilt each little piece. Fusible isn't forever and it needs the stitching to keep it in place. To get precise placement of each piece of fusible, use quilter's plastic (inexpensive at Joann's) and a fine-point Sharpie to draw the pattern out on...place the plastic over the design to make sure that you have placed each piece perfectly before pressing each piece. Slow, yes, but it does create perfect placement of each piece. I am working on a fusible applique quilt for my bed right now and since it is ash gray for the backing fabric, I know I will be washing it often. I did blanket stitch around each piece. You can see a picture of the top here:
http://farmquilter.blogspot.com/2015...-finishes.html