I'm able to control aiming very well for TS2, mostly because I never "aim". I found the aim-control (clicking the left shoulder button) is incredibly jumpy, and so I just go by the center of the screen. Sure, you can't snipe people that way, but I don't like camping levels.
But yeah, if you can't use the C-stick, try swapping controls, or try to play a few deathmatch rounds against bots without using aiming (just shoot at the center of the screen). The thing I really like about using twin analogs for FPS is the analog movement control. However, for some reason TS2 is a bit on the twitchy side regarding control, so it does take a little getting used to to get really good (which I'm not).