Sairsk,
There are a couple factors that bear on methods like what is the orientation of the opening relative to the bend, up like V, inside like>, or outside like<? How large is the radius? How large are the flanges of the channel? What kind of bender do you wish to use? Have you talked to Tools For Bending to see if tools already exist? Can some portion of the channel have a controlled distortion? Is this extruded channel or formed?
Without details, we could write volumes and still not answer your problem. Bending shapes seems to be more a matter of control than overpowering.
Griffy