I use a baking soda and milk mixture. About a tsp of baking soda mixed with half a cup of milk. Dip a Q-tip in the mixture and clean off the mildew. Don't double dip the dirty Q-tip back in the soda milk, though. Use a bunch of Q-tips until you've cleaned it off. Then add more milk to the mixture and a tsp of hydrogen peroxide, and spray the plant thoroughly -- underside of leaves, too. Let it dry. Then spray it again with de-chlorinated water to wash it off. If you have more than one plant, keep your sick plant isolated from the others until you are sure you've eradicated the problem. And -- you need to figure out why you got the mildew to begin with. Too much watering, perhaps?