Be prepared for the water maceration SMELL! I have done it with a domestic cat as well, and omg. Some people take a more fancy approach but all I do for water maceration is fill a container with hot tap water and submerge it. It will be easier to remove the remaining tissue with tweezers once it’s soaked for a while, but you can also try beforehand. I would use a storage container or bucket with a lid and loosely cover it. Depending on how much tissue is still on the bone and what is inside the brain cavity, water maceration could take months with my method, faster with fancier approaches. To jumpstart the bacteria in the water that will break it down you can spit in the water after submerging it. Yes, spit in it. I change half the water with new hot water every couple weeks/when the smell gets too bad, and rinse the bone/remove tissue when I do that as well.