Yeah, it is a little bit complicated. I'm trying to make a realistic looking terrain in a map atm. It needs a lot of time and BSP isn't happy about a too much complex structure, but it's possible.
I don't know the cone tool. Maybe it will help a little bit. But is the brushwork really clean? I guess making it by yourself will be more effective
There was also a terrain model, I believe. The problem is that you can walk through models, they don't block you.
So, if you are new in BSP, try to make easier and less complex maps first.