I have heard that rubbing a cut potato on the interior of the visor and wiping off, or the same with dishwashing liquid can reduce the fog effect.
I can see where the potato technique might give you a few more eyes...(you're carrying the MASH thing too far)
A thin coating of dish soap has been proven sort of effective, but the hard truth of the matter is that in order to see clearly, you're going to need something like a Fog City anti-fog insert (very finicky install, but if you get it right I had one last three years) or the Pin-Lock system.
Pin Lock adapters are standard on high end helmets like Shoei, HJC etc. but you can adapt most visors that don't have radical compound curves by doing it yourself. Pin Lock shows you how to do it.
Both Fog City and Pin Lock eliminate fogging by trapping a dead air space across your visor; a sandwich between the insert and your face shield.
Both the Fog City and Pin Lock inserts run about $30-$40 USD. In order to use the Pin Lock insert on your current helmet, you'll have to use the overlay provided by Pin Lock, drill two holes for the locating/anchor pins, and then insert the pins. The faceshield insert then locates to the installed pins.
There are any number of opinions and witch doctor approaches to anti-fog, but these are the two that have let me operate safely in cold, rain and fog. (Of course most of the time I keep my eyes closed because the sight of the road and traffic is so scary