A pizza oven mostly cleans itself if you burn it hot. The brush is for the cheese that did not carbonise and the flour you left in the corners.
Ooni’s 2-in-1 is the one sized for a Koda or Karu: sweep, then flip to scrape. Wear gloves. Do it when the stone is warm, not white-hot. Do not soak the stone. Do not soap it.
If you only bake on a kitchen steel, skip this and buy a scraper.
Buying guide: How to clean a pizza stone, steel, and pizza oven