Combine the first 4 ingredients and let stand in a warm place until bubbling nicely. In a large bowl, stir together 1/3 cup Sugar, 2 1/2 cups Water, 4 cups flour, and 3/4 cup dried skim milk. Stir in the yeast mixture, beating well. Cover the bowl and let stand in a warm place until the sponge is well risen and bubbly. Add 3 cups warm water, 5 teaspoons salt, and 1/2 cup lard and beat well. Stir in 6 to 8 cups flour, mixing until the dough clears the bowl. Spread the remaining 2 cups of flour on a pastry board, turn out the dough and knead well, using a little additional flour if necessary to make it smooth and satiny. Return to the bowl, dust top of dough with flour, cover with a damp cloth and let rise in a warm place for about 30 minutes. Turn out. Knead thoroughly, using only enough flour to keep dough from sticking. Divide into 6 even portions. Shape into loaves. Place in greased pans. Brush tops of loaves with soft lard and allow to rise again until double in bulk. Bake in PREHEATED oven for 45 minutes; the first 20 minutes at 425 F.; then reduce heat to 350 F. for the rest of the baking period. If a very soft crust is desired, brush top of loaves with melted lard or butter as soon as they are removed from the oven and allow to stand for about 5 minutes before removing from the pans. This recipe makes 6 medium size loaves.