Now this is what I am talking about:



It would take a long while to get any where but the over all work would be well worth the effort. And would have to switch over to this when arms get to tired from rocking back and forth



Then when they are close to death make them spend time with this:



By the time Ben is done boring them to death and showing his piss poor acting skills you will end up with this:



Now for all seriousness, even though the cheese grater really scares the shite out me I would have to say quick and almost untraceable would be the way to go about it. Something like a fully charged phosphoric acid bath. The only thing left in the end will be the fillings in your teeth and the soles of your shoes. There is no escaping either because by the time you hit the acid the electric current that runs through it would kill you instantly.