Flock & Mica
Use Double-sided Adhesive (Markers & Tools):
Use a pencil to mark the shape required on the adhesive backing, cut to shape, remove one side and add Glitter, Mica or Flock. Depending on the finished required and the thickness of the adhesive either remove the other side or use an adhesive to secure in place. Some thin double-sided adhesives are more transparent than others.