I have made them several times
I have found that a whole container of icing was too much. I end up using about 1/2 - 2/3 of a container. Also, I prefer using chocolate cake. The red velvet is too sweet not to mention your hands look like you've 'gutted' some thing. I use golves now not matter what type of cake i use. I first did this a christmas following some of bakerella's ideas tree, santa hat, reindeer, etc. for gifts and then again at easter. However, I am not as talented or artistic as bakerella and the pics will never be shown smileys/smile.gif
I have also done just the balls.
People go crazy over them.
I don't see why you couldn't use your own home made icing - just more work for you.