I did see some benefit from the manganese-based spray products (ACS or Rutland) back when burning a smoke dragon through the clay-lined flue. It had to be used heavily and religiously along with hot, high throughput fires and sort of changed the glazed creosote to something more brittle or flakey for easier removal by brushing. The ACS logs also rely on manganese but cannot get the upper flue to the required 300 degrees needed to activate the chemical reaction. The danger with these things is that the user may think that they are a substitute for brushing (definitely wrong). Now with an EPA Stove, SS lined flue and dry wood (burned hot) these pruducts are a waste of money.