For a double layer round cake, use tooth picks to keep the top layer from sliding off & also place in the frig.

I use ready made frosting all the time but I put the frosting in my mixer and whip it up and it spreads very easily.
I usually use about 2/3 of a container for a 2 layer, 9 inch cake. Most of the time I use the chocolate flavor type.
Store the left over frosting in the fridge and use it for cup cakes.
Grands love the cup cakes better than the layer cake...

...or keep it in the fridge for when you need that little spoonful taste of chocolate! {{{{wink}}}}

I also nuke my frosting when doing a bundt cake, it drips down nicely, and there's plenty of leftovers for the midnight chocolate fix.

I mix one large box of chocolate pudding mix (or whatever flavor you like) with one quart of whipping cream and whip it with my electric mixer until it gets kind of stiff and fluffy. Not low calorie but I could eat a tub of it! I have used this for frosting on cakes and filling for pies and tarts. Must be refrigerated.

MaryStoaks I do like the sound of the pudding and whipping cream -- got some grandsons who will love it. Thanks.