Canon 580ex Flash Unit
When one wants to use manual flash mode in modern TTL flash units that have?

Could one use this mode with a flash of camera only and not other types of lighting, or is it used when you want to use your camera flash to add fill flash (fractional power settings, that is, half the power 1 / 64, etc) along with flashes of study (ie, Elinchrom, Broncolor, etc.) What is the process step by step to setting camera and flash? My camera is Canon 30D with 580EX flash.

You could use the manual mode on the flash if you are in a defined position and are flash taking meter readings. Usually, you will do this if the flash is off camera, controlled with something like a pocket wizard. When you use it in camera with TTL, it is best to put the camera in manual mode. It is difficult to explain in few words, but here is an excellent resource. I recommend his book on the use flash. It is by far better results when using the camera flash. http://www.planetneil.com/tangents/