I have done a few. I use a firm cake and make sure I give it a good crumb coat. I make the icing a bit thinner for the crumb coat so it will go on easier. Putting it in the frig. for a few minutes to firm it up, is helpful too.
Sorry you had to deal with someone like that. She is the type of customer that made me stop for a while. I now do only for friends or family. Just take a deep breath and remember all the others who love your cakes.
I'm am in the process of icng the last of 23 8" rounds for a wedding and noticed my first 10 are now sitting in what looks like melted butter. I have never had my bc break or weep before. What if anything can I do? The wedding is tomorrow.