info_no_dynamic_shadows exists and you use it by selecting faces, and no shadows (pickups or players showing through walls, etc) will appear on that face.
I quick thing I like to do is set the scale of all my tool textures (trigger, hint, areaportal, skybox) to 10. Not 0.10, but 10. Basically, fuckin huge. It makes it a lot easier on the eyes.
If you have a brush inside another brush, and you want to select the brush inside, select the brush outside and keep the left button pressed until the selection switches to the other brush.