It always (well, almost always) works for me. you need to make sure that the section fill is the same for the objects as it is for the walls, slabs, roofs, etc. I do this all the time and only occasionally do I have a line that just won't go away.
I typically have walls, slabs and roofs all meeting at the eaves with a library part for the cornice trims. I have no trouble getting them all to make a clean outline in section. To keep it simple (and easy to remember and teach others) I use a fill that I call "! Section Fill" for everything that I want to clean up in section. (The exclamation point puts it at the top of the list.) It is a copy of the standard "Empty Fill" which has to be merged into AC8.1 files (if it's not already present) since we can no longer make copies of the solid or empty fills