>>713117725
You don't model in Trenchbroom, but instead place brushes in a grid which is way, way faster. You drag your mouse to create a brush then resize it until it looks like you want. There are also tools for cutting them or manually moving it's vertices, edges or faces if you so desire.
Just recorded this for you, making a little bridge and a room takes no effort at all. If you want to learn more about it I recommend this YouTube channel:
https://www.youtube.com/watch?v=gONePWocbqA
As this anon says >>713118068 you can also apply some logic and place entities but I don't use that, at least not for now.