If I have complex building or walls.
for example if I have an L shape window I create an L shape Portal, which I do not know if its correct, but it works.
Sometimes if the portal does not do too much, or not working the way I want. I just put a plane light and pushing a bit more light with it. Straight into the interior.
Think of portals and light planes as a extra help for the engine to concentrate the light samples where you want them.
For example - working for 10 years with vray IM+LC.
Sometimes with detailed classic window frames you get splotches around and in the cracks. When you put a vray light plane in front of it and include only the frame into that light, set it up as a very low intensity just to push more information there - and boom no splotches. Because you just gave your render engine more info to work with.
Of course with BRUTE FORCE we do not have splotches, but lighting wise its almost the same aproach.
Its like interior photographers they put fill lights and stuff everywhere to make the shot right. Because camera is not like a human eye. Its primitive.
And render engines are the same. A lot of things will not work like in a real life. And I will not even mention the render times with some "real life things" :D