You can find at gun shops a product that is called Tru Oil, actually it is not an oil, it is varnish.
They apply it at the wood parts of the guns to protect them from cracking after continuous use near water, I am talking for hunting guns of course and not those AK-47 Kalashnikov
You apply the product with a rag , one hand every two or three hours, easy to use and when it is hardened it gives a nice yellowish color to the wood.
https://www.amazon.com/Tru-Oil-Stock.../dp/B00FSVM06S
The other option is clear varnish in a spray can...