[RUNGSI]

Well,
Making a brush detailed and what it does:
Basiclly to keep it simple. when you make a brush detailed its telling the compiler to ignore the surface when its creating its leaf nodes.
the VIS size is the amount of surfaces that the compiler will need to use in order to make its leaf nodes.
a leaf node is an invisable box which tells the computer what surfaces to draw when the player stands in that location.

Now, If your VIS size it increasingly high and you dont have the time.
Yes making everything detailed will save you time, But making everything detailed will reduce the performance of the map.
You would get better results by just running a fastVIS when you compile the map, if time is an issue. Your framerates will be better then having the full map detailed.

What I usually do is, Make sure all my models, enititys on the map are set to detail. You must check the box in the enitity window.
Anything in the map like trim or sections of walls that are broken, set those to detail.

always look to see if you can reduce the amount of brushed before you start going crasy with detail.
Detail is very good, but can also reduce performance.

I keep all my walls, floors, ceilings, ground as structures.
any type of decor such as boundry walls, broken walls, rubble, molding, small brushes. thiings like that.. i make detail.
And always set models to detail..