There’s some good threads on here about cleaning mohair hoods, like this one.
I have largely followed the same process as @Dipstick - soak the hood down, fill a bucket about quarter full, add soap/shampoo and a good squirt of Milton fluid, then massage it into the hood with a soft-bristled nail brush in an area of about a foot square at a time. Rinse it down, then move on. Once you’ve done the whole hood, go back over it until the gunge stops coming out. Holy cow, did that get a lot of muck out of the hood! I part-opened the hood to let me get all the way down around the bottom where it meets the car - an old toothbrush helps - and, judging by the amount of muck in there, it was well overdue for a clean. You do have to be a bit careful with the hose, but it will drain fairly normally without soaking the inside.
After drying in the sun, I use the Autoglym sealer shown above. I did try the cleaner part of that kit, but the above method seems to work much better.
Best done on a warm summer day when you don’t mind getting wet!
Final step is to pull through the drains if you haven’t already, and I also get down and make sure the little drains in the bottoms of the sills and doors are clear with the end of a small cable tie.