Combine 2 cups flour and 1/2 teaspoon salt in medium mixing bowl; cut in shortening with a pastry blender until mixture resembles coarse meal. Sprinkle half-and-half evenly over mixture; stir with a fork until all ingredients are moistened. Shape dough into a ball; chill.
Combine sugar, dash of salt, and remaining flour; add butter, lemon rind, and juice, stirring well. Fold in blueberries.
Roll pastry into a 12- x 8-inch rectangle on a lightly floured surface. Spread with blueberry mixture. Roll up jellyroll fashion, beginning at long side; moisten edges and ends with water to seal. Transfer roll to a heavily greased 15- x 10- x 1- inch jellyroll pan. Bake at 425° for 40 minutes. Cool 5 minutes. Transfer roll to a serving platter.
Combine powdered sugar and water in a small bowl, mixing well. Drizzle glaze over warm roll. Slice and serve immediately.