Just found "how to make a stencil" in one of my quilting mags. Trace design onto blank paper........put bridal tulle into an embroidery hoop.........trace design onto tulle with a permanent marker............leaving tulle in hoop place in desired position on quilt.............trace design onto quilt with a washable fabric marker of your choice.
This seems to work on all but the darkest fabrics. So much easier that cutting out plastic.