Differs from a fart baloon only in the way it is blown up. You stick a straw up your ass, connect a baloon to the straw and let loose with a long powerful fart.
Have your friends watch in amazement as you blow up fart baloons using the fart baloon II method. It helps immensley if you gorge yourself with a meal consisting of a lot of spicy mexican food, brocoli, and deviled eggs 2 hours before you start. Fart baloons will float for a week longer than baloons blown up with helium. Also, if you breath in a fart baloon your voice sounds even funnier than with helium!