I agree with ckcowl. Chose colours that blend with the applique. Practice on a scrap with same thickness as quilt sandwich to set stitch length and " swing" of needle left. You want the swing shallow, so it just catches. The length is best set longer than used for piecing ( try 3 ). Sew slowly, using clear open toe foot, gently pulling applique away from background so you are truly in the ditch. You will be amazed!!