I didn't dig out the brains, eyeballs or even remove the tongue or lower jaw - just took off the hide and put it in the hole.
I've got very rich soil with a whole bunch of different ground critters that seem to eat everything but the fat which washes right off with the garden hose. No scrubbing, scraping or cutting. The brain cavity was clean as a whistle but some chunks of stuff did come out of the nasal opening when I hosed it off. All the thin little bones in the nose are intact.
This isn't how I'd do it if I was going to display it in the house. The bucks and bull that I have in the house were beetle cleaned, decreased and whitened by taxidermist. When I do it this way they look more like you found them in the woods which is a look i also like.