Using dough hooks cream margarine. Add vanilla, salt, sour milk, buttermilk and flour. (dough should be soft and not sticky).
Divide dough into 6 portions. Roll each portion into a rectangle, about 9 x 13. Fold into thirds lengthwise (9 x 4 1/3)
Put into refrigerator several hours or overnight.
Roll each portion very thin into a rectangle measuring 28 x 7. Cut into 1 inch wide strips 7 inches long. Roll around foil covered round clothes pin, overlapping a little.
Bake 15 minutes at 375 degrees. Let cool a minute and then slide from pin.
Mix 2 cups milk and ¾ cup flour. Cook over low heat to make a thick paste. Cool completely.
2 cups Crisco, 2 cups powdered sugar, 2 cups granulated sugar and 2 tsps. Vanilla extract. Mix a long time until smooth texture. Add cool flour paste mixture and mix well. Add 12 tablespoons marshmallow cream. Use pastry bag to fill lady lock.