Using emery cloth...?

You have other options that could get the job done faster and more efficiently. You could go with a sawsall with a metal blade, or a power grinder. Trying to sand it down will take days. If you don't have these tools available, or don't know anyone you can borrow them from, you could call your local tool rental. A sawsall, or grinder are hand tools. Rental would probably be pretty cheap. It would likely be worth the time, effort, and frustration you'll save.