I've never heard of a cotton yorkie before here in Iceland.
The yorkie breed should only have silky coat not cottony.
1. Fido has silky coat (normal yorkie coat) , but he has very thick coat and after he was shaved this summer he started getting cottony coat above his tail, nowhere else just above the tail.
I always put silk drops there to get the coat there silky again its not working really well.
He has the thickest coat i've found on a yorkie, but not cottony (except that small place above the tail).
2. I use Pet Silk, shampoo called Pet Silk Rainforest Shampoo and conditioner called Pet Silk Rainforest Conditioner, then after baths i spray on Pet Silk Leave In Conditioner after and brush it trough the coat
Then sometimes after bath i don't use the leave in spray but i use Pet Silk Liquid Silk Serum drops and rub it into the coat, i love that product.
3. I wash his coat every 5-7 days it depends how well i wash the coat and how dirty the coat becomes, sometimes i bathe him with 2 weeks between the baths sometimes just 5-6 days, it depends.
4. Either totally shaved, but just hair on the head and feet, or fluffy everywhere with long coat, if the coat is medium length it gets more matts than if its in full length.
He has so thick coat that i groom him twice a day.