I've made art quilts with silk dupioni. I machine applique and found that if I wait till I need the applique piece to cut it, I can just about get it sewn in before the fraying gets too bad. I don't back it with anything just stitch it down. I do a stay stitch (like in garment making esp. around neck openings) using a matching thread right along the edge before sewing the applique. The satin stitch I use covers the stay stitch.