i tested it out with a bugatti car model i had and got it to work without any bsp/errors.
Its very simple you can select Brush >> import, and then you can just select the obj file you want and use it to add or subtract. Or if you want your entire map exported make a big brush bigger then the entire level then ctrl-alt drag all brushes including your red builder brush and select intersect or deintersect and then your red builder brush becomes your entire map wich you can export as t3d or obj file to use in your next map or Autodesk Maya.
i figured you need to select right click >> transform permanently and or polygons >> snap vertices to grid before adding/subtracting your new brush to avoid bsp error's in Unreal editor.
don't know if this is new to 469D patch or if it was possible in earlier versions.
so you need the brush >> export and import option, (save brush and open brush is something else) need export/import option.
