Dissolve yeast in warm water in large bowl. Add sugar, shortening, salt and 2 cups of the flour. Beat on low speed, scraping bowl constantly, 30 seconds. Beat on medium speed, scraping bowl occasionally, 2 minutes (or beat 300 vigorous strokes by hand). Stir in remaining flour until smooth. Scrape batter from side of bowl. Cover and let rise in warm place until almost double, 40 to 45 minutes. Stir down batter by beating about 25 strokes. Smooth and pat batter in greased loaf pan, 9 x 5 x 3 or 8 ½ x 4 ½ x 2 ½ inches, with floured hand. Cover and let rise until double, about 40 minutes. Heat oven to 375 °F. Bake until loaf sounds hollow when tapped, 40 to 45 minutes. Brush top with margarine. Remove loaf from pan; cool on wire rack. *If using self-rising flour, omit salt. Also, unbleached f