There have been several people who got motor oil and other products in their pool, but I've never heard of getting an entire grill into the water. The ash is something that has to be physically removed, probably through a combination of skimmer socks and circulation/filtration/backwash/clean. As for the organics, including grease, I'd suggest using an enzyme product such as Natural Chemistry® Pool First Aid™. If there's a LOT of oily substances on the surface of the water, then you can use absorbent mats from New Pig or AbsorbantsOnline.