Place shortening in large bowl and beat with an electric mixer on medium high for two minutes. Add the butter and beat until combined. With the mixer on low speed, gradually add half the sugar. Add the milk and vanilla. Beat on low for a few seconds. Keep mixer on low and add the remaining sugar. Cover mixer with a cloth, turn the mixer up to medium high and beat for 2 minutes. Add more milk if it's too thick. To decorate, use a plastic disposable pastry bag (I used Wilton brand). Cut about ½-inch off the tip of the bag. Insert a 1M pastry tip (Wilton). Fill bag with frosting, about halfway full. Pipe frosting in a circular motion, going around a few times until you have a nice amount of frosting. Decorate with sprinkles if desired.