I made mmf on Saturday, with a little corn syrup added to belp with pliability, wrapped it up good, and left it on the counter.
Today, I opened it up and started kneading it with shortening on my hands and the table to get it pliable enough that it wasn't cracking as I kneaded it.
I ended up having to reroll a couple of times, and each time I worked more shortening into it because it had dried out while I rolled it.
I finally got it rolled out mostly good, but by now it was so pliable that the smallest bit of pressure left an indent, and when I tried to pick it up to put it over the cake, it just tore all to pieces under its own weight.
What did I do wrong, and how do I fix it so that it both has integrity and doesn't crack so that I can roll it out smooth?
I've never covered a cake wih fondant before, although I have used it to make a base for my royal icing church, and I covered a cake pan with it for practice, and neither time did it seem like it was going to be so difficult to work with.
Sounds like you worked too much shortening into it. You can add more powdered sugar to help firm it up a bit. Add a little at a time so you don't add too much and make it dry.