The Saffire comes with a beautiful Cast Stainless Steel Exhaust Damper, and it is a hefty, impressive piece!
Another reason I LOVE kamados... 9 months of heavy cooking, and we have to spend less than 30 minutes doing a deep clean. No rust to deal with, no pressure washing the inside of a greasy pit, no scraping of carbon build up (very rare)... just down right simple.
You could also clean it by putting it in a 500f+ grill for 15-20 minutes.
And leave the top damper open without the ability to shut it down?
Good point. I clean my top vent in my gasser so it's not an issue. You could close the bottom vent and put a cast iron pan or brick on the top vent to shut it down. But if you don't have a gasser, your method is likely the safest.
I have found for cleaning oven racks & grill racks, place them in a plastic tote or anything large enough so they lay flat.
Fill with hot water enough to cover racks. Add some dishwashing detergent like Cascade.
Leave overnight & wipe clean in the morning.