|I got this tip of reinforcing Patterns with Plastic film from a Singer book called 101 Sewing Secrets. It works well with dry-cleaning bags and I used plastic freezer bags that I cut open. You sandwich the plastic between tissue paper backing and the pattern side up, and with a dry hot iron press slowly over the pattern. Turn over and press again. Check to see that all areas have adhered. When cool, trim excess tissue paper and plastic film.
As a precaution against getting melted plastic on the hot iron, cover the exposed plastic with another layer of tissue paper.