Most people that have something like this use it shortly after grilling to stripping away any char buildup and leaving bare grates until the next time they grill. This is actually not that great for your grill. The char acts as a protective coating and prevents the grates from rusting. Cleaning it also leave less time for the flavor to bake into the grates if you're the type of person that believes in that.
I'm sure the product does what it is designed for, but its a better idea to just leave the grill be once you take you meat off and leave it. When you want to use it again get it up to temperature then clean with a hand brush for easiest removal.
Source: I used to sell really expensive barbecues to rich people.