Combine flour, salt, sugar, and shortening together with pastry blender.
When blended, take out 1/2 cup of crumbs and reserve.
To remaining crumbs add baking powder, cinnamon, and nutmeg, and mix well.
Then add milk and eggs.
Pour into prepared pans.
Sprinkle reserved crumbs on top.
Bake 20 to 30 minutes or until toothpick inserted in center comes out clean.
NOTE: All you are trying to achieve with the sour milk is the necessary acidity for raising as sour milk reacts differently with baking powder than regular milk. The intention is for the milk to sour, not curdle -- if it curdles slightly it's not a problem. You could achieve the same result substituting an equal amount of buttermilk. However unless you have a use for the rest of a quart of buttermilk, most people prefer to use the lemon method and sour just enough regular milk to use in the recipe. Just add the lemon to the milk while you are getting the dry ingredients ready and it will be just fine.