There are already some great responses, but I want to add that one effective way to coach senior employees is to give them responsibilities one level above their current role and then provide feedback.

For engineers aiming to move into management or staff engineering, you can assign them a project at the level they aspire to reach and give feedback once they complete it. For example, for an engineer aiming to be an EM, I expect them to lead not only meetings but also all communications related to this project, while I act as their director. Afterwards, I provide feedback.

It doesn't have to be that extensive right away. You can start small, like asking them to lead a roadmap meeting, and then increase responsibilities as they improve. Essentially, create a safe environment for them to grow.