There are two methods I have used and both work well.
One is another product, called CatCrap. Its a real product, and can be found at REI. Small little dish of lens conditioner. It takes a bit of work to use it, rubbing it on, letting it dry, then buffing it off. Works best if applied twice.
A cheaper method that works wonders and needs be reapplied after getting them wet, IE rain, is Dawn Dish soap. Applies the same as above, however if you use a hair dryer to dry it to a haze, it drys faster. Just a very thin film of it over the lens, then dry it, buff it well, then your good to go.
Keep in mind, this method although very successful will not work after being subjected to water as its water soluable soap. You will need to clean the lens areas and reapply if you dunk em, get in in the rain, or just wash them if your so inclined to do that once in a while.
To test this new concept to you, try it out on your bathroom mirror in a spot, then apply hot steam against the mirror. You will see the area that was treated will not fog, or will not fog nearly as quickly or to the same extent, based on the level of steam applied. For this test a pot of boiling water held up near the glass to steam it will work. Using a steam generator device such as a SHARK mop would not be well advised, due to the nature of how it works it would just clean off the mirror all together. LOL
Have fun, try it out.