I thought I would follow up my suggestion with some notes.

In this image, I show a simple stairway on the right. On the left, in rose glass, are the intersects for the railing posts. The second from the left shows in green glass the posts and rails, which would be positive. Group the positives and the intersects (and change the materials) and you get the post and rails seen in the third from left. This is much easier to do than making individual posts and rails.