I know a very usefull texturing technique. It goes like this:
Lets say you have an arch like this:
This object is 256w 256l 160h, made out of 12 brushes, with a wall witdh of 16. The used texture is C1A0_LABW4.
Lets say want to retexture the top faces (marked red):
Lets apply a trim texture on those faces. I picked OUT_WALL2C. Go ahead and apply that texture to those top faces. You'll end up with this:
That looks horible so you need to rotate each face. This is done by selecting a single face, and start messing around with the toggle texture application. When you have once face alligned well, go for the next one. But you might all agree with me that this takes an awfull lot of time. There is in fact a very simple and quick way to get all those faces alligned. Here it goes:
First, apply the OUT_WALL2C texture to all the inner faces of the arch and make sure their're rotated 90 degrees. You should end with this:
And now for the magic spell. Select one inner face, hold the ALT button and right click on the opposite face. Like this:
WAOW! Nice eh? Do the same with all the other inner faces. Then just retexture all of the inner faces with the original texture, which was C1A0_LABW4. Dont forget to set the rotation to 0. You'll end up with this:
There you go.