TTL flash exposure typically requires that all flashes are compatible with a single TTL system, and it's not clear from your description which if any of your flashes would work with TTL. Manual flash exposure is a bit more work, but is will work with virtually any flashes. If you don't know how to perform manual flash exposure, Strobing 101 is a great place to start.

Studio strobes often include a "modeling light", which is a small, always on, incandescent light whose brightness is scaled to the strobe brightness. This allows you to easily preview the effect of the strobe without taking a picture, and also provides enough light for autofocus or manual focus.

Many cameras, include the Canon T2i have an AF assist lighting system, that when enabled allow the camera to achieve autofocus, even under ambient lighting conditions that are too dim for effective autofocus.

Finally, if you use a bright flash combined with low ISO and your maximum flash sync shutter speed, you should be able to have ambient light that is bright enough to focus with, but that will not contribute significantly to the final exposure. You can confirm this by taking a picture with these ISO, shutter, and aperture settings and with the flash temporarily disabled. If ambient lighting still shows up in this exposure, reduce the amount of ambient light, reduce the aperture, or lower the ISO until you achieve low enough ambient lighting that you can still focus by, but does not contribute significantly to your exposure with the flash disabled.