I have not checked out what the Rain-X is about but normal lenses with generic anti fog wipes does not help sweaty old me. According to the optician no anti fog agent works because of the basic physics. The difference between the Optifog treated lens and a normal lens is that the surface is different. An untreated Optifog lens actually fogs up more than a regular lens. But that is not how those glasses are designed to be used. Together with the activator the Optifog lens coating distribute the small droplets that make the fog on the lens if allowed to accumulate like in a normal lens. Here is the beauty of the Optifog treatment+activator designed for the coating -they work in tandem to distribute the droplets into a thin see through film on the lens. Just like the one in your eye an even water film is clear see through non sight obstructing goodness. And at least for me climbing on a course that is built around in a ski jumping hill in the snow with rain for almost half of the first round at 34 F it worked so well that i never got any fog at all. None whatsoever. The rain drops came in too quickly and are too large to immediately spread into a film but after the rain stops it seems to take two minutes to get a perfectly clear vision unlike with normal lenses.
The optician told me to try on a generic anti fogging wipe he carries called Prosben on top of the activator but so far i have not found a need for that because the activator+Optifog coating works so well