Over the last few years, just for fun, I have treated the underside of several mower decks (including brand new never used) with several of the sprays and a few of the brush-on deck coatings. I have prepped older decks by scraping and scrubbing them clean and I have coated a brand new deck before its first use. And all of the results were short lived. I could get a couple of mowings with no build up and sometime just slight build up but after 4 or 5 mowings it is always completely gone. That doesn't mean it's a total waste of time. If you it helps and you have the time to spare ...go ahead. But it will need re-coating pretty quickly. It definitely helps with deck build-up and helps keep the deck from clogging but not for very long. The big benefit is ease of scraping the build-up after mowing. It is probably not worth it considering the time and effort required but since I have a MoJack lift, this year I may keep a can of the spray around and after one of my cleanings just give a quick spray to assist the next clean up. The applications help keep the wet grass from sticking but I have concluded that I need to scrap anyway. I saw no difference from spray coatings and brush-on coatings or from brand to brand. If someone has been successful with a coating, please share as we ALL would love to hear about it.