You can assign people to a list and then when you create a post, you can set individual posts so that they only appear to a specific list or lists (or even just to specific people). You can also set up posts so that certain people or lists CAN'T see it.
When you type a post, just click on the lock next to the share button and select Customize. Then, on the pull down menu next to These People, click on Specific People. If you have a list created, you can type in the name of the list and only the people in that list will see your post.
It all obviously takes a few steps - both creating lists to put people in and setting up parameters for specific posts - but it can be done.