Training new staff is somewhat like preparing for some of those SAT questions that ask “what’s next in the sequence?”
You can only study so much for the SAT, just as you can only share so much information with your new staff. Neither can have the goal of knowing all of the answers.
What you’re really after with employees is for them to understand the context enough that they can pick the behavior you’d want them to choose based on your mission and values. Help them understand the “why” of the initial information you share so that they can correctly choose what is next in the sequence.