In a large bowl, but shortening with an electric mixer until light and fluffy, approximately 1-2 minutes. Add one cup of powdered sugar to the shortening and beat until well combined. Add vanilla and salt and mix until well combined.
Add in another cup of powdered sugar, and beat until well combined. Add in a small amount of the milk, and mix until combined. Repeat this process with powdered sugar and milk. If a thicker frosting is desired add additional powdered sugar, 1/4 cup at a time, beating well after adding additional powdered sugar. If a thinner frosting is desired, add additional milk, 1-2 teaspoons at a time.