Well first of all, what static are you making this .occ mesh for? Not all statics should have .occ meshes, only the ones that are large enough to commonly block the view of other objects behind them, which basically comes down to large walls and large buildings. If the large building is enterable with lots of windows then making .occ meshes for them can be a problem and in some cases not possible as otherwise you could stop the players within the building which you could see though the window being from being drawn, or the landscape behind the building that you can see though two windows though the building from being drawn. If the object is too small like a low wall that will only fully hide stuff when you are fully prone behind it probably isn't worth making an .occ for as it will do more harm than good performance wise as calculating when the .occ is obscuring an object or not takes some effort, but if it hides significant stuff a lot of the time that generally pays off. As such you need to ask yourself, and probably us too to begin with if this is the right object to make an .occ mesh for
As for making them, they are really just a series of quad planes (can't use tris) on the very edge or inside of an object with each quad plane acting as its own barrier to my knowledge.
Anyways here's the muttrah_houses_1b in BFMeshView:
Here's its .occ mesh:
And here's them together (done though photoshop of just taking a ss of both from the same view then blending them together):
In this case its just a simple box, missing off the extra bits from the larger part since its not worth making another box to cull those little bits and note its inside the balconies etc as players can walk on there.
You can look at other .occ meshes with BFMeshView in the same way which you can get from here if you don't have it:
BfMeshView
You can also view them in the editor but it isn't as good. But I normally use the editor for testing, although note the level editor won't take into account object movement so you have to save the object in its location, then reload the editor in order to test it fully otherwise the .occ mesh will be left where the object first began, if just put into the map, where you first dragged and dropped it in but testing though the editor dose mean you can test things like props inside a building, although you may need to remove many faces of the building in order to see if its actually working as if its a good .occ mesh, you won't be able to tell without
As for exporting, this script will do it, can't fully remember how since I use a modified, automated version of this script myself that exports the static with the .occ mesh being part of it, but from memory you select the mesh, run the script and then put in the scale and the dir to the folder and the objects name and hit export. But can't remember fully but its very important to test as the scale setting isn't always right by default, depending on the units of your scene etc.