I have used no-melt mylar for circles for applique, but I have found that for odd-shaped pieces, it doesn't work as well. I have used a large basting stitch, (leaving a couple of inches of thread at the ends),place the mo melt mylar in position, then pulled the strings to shape around the plastic, and iron on the right side of the fabric. When I do this, I leave the plastic in, until ready to apply to the piece to the background fabric