You can use the fusible interfacing for your medium to large applique pieces. Eleanor Burns show the method in many of her patterns.
Yor sew with a small seam allowance around the outsides of the piece , withe the fusible side facing the right side of the fabric piece. Clip th curves and turn it right side out. That puts the fusible on the proper side and leaves the edges of the applique nicely turned under for sewing, after the piece is ironed into position.