To add a little more pop to your kendama's grain and to improve the durability of the wood, using conditioning sealant can do just that. Wood conditioning is a common practice in the woodworking world, as it is used on furniture to help cover and prevent oil-based stains, and to improve the wood's cosmetic look.
In the kendama community however, we call it Kenditioner (for obvious reasons!).
Kenditioner is a wood conditioner wax that is naturally based as it is usually made with coconut oil, beeswax, and honey type products. When applied to a kendama you'll notice the wood to get more vibrant.
Wood conditioning is perfect for full natty kendamas or just the ken. Other alternatives that can condition kendama wood's are butcher block wood conditioner, and just plain beeswax. In the past we have seen fully natty kendamas with just there tamas having beeswax applied to have a 'rubber' texture.
We met a player once who took a large chunk of beeswax and stuck it to the tama. He then used a hair dryer to melt it as he spread it around the tama. After a few layers were applied the tama did indeed feel like it had a natural rubber paint texture, making the natty kendama easier to play while still remaining natty. So in all, conditioning your kendama is just another way to enhance your kendama and give it an extra layer of durability and grip. It is one of those things in kendama that is a players personal preference, so it doesn't hurt to try Kenditioning at least once!