As their manager you need to do 2 things:

1. Learn to embody their tone. You’re selling them & their subject matter – so you should be a ‘mini expert’ to get their content most of the way there for them to just audit or tweak for any added commentary
2. From there – you can either take their unique point of view and build evergreen content like quote graphics etc. & or find current events for them to easily comment on (linkedin trends are a great place to watch for relevant material that is industry relevant).