There used to be a lot more discussion about his products, maybe because they aren't new anymore the discussion has died down.
According to posts by Bill many times, he has said that when sprayed upon a fungal infection you can actually see it melt away within a few hours in many cases.
The bottle indicates that you should put down 3 oz/k for curative and 2oz/k for preventative. I believe it says to apply approx every 14 days or so....so basically it is like an inorganic in how often it is applied.
Here's a link from Purdue, which is close enough imo for you to use as a guide for WHEN to begin applying...I believe it says when the soil temp reaches 65.
In the Chicago area, the soil temperature at a depth of 4 inches is currently 50 degrees, so it is too cold for the first application if you follow the Purdue guide.
EVERY operator here would suggest that cultural practices designed to improve the soil and environment for the turf is the best long term solution to the problem. You probably already know that though.