Takes time but what helped me the most is my new matte screen overlay. The 3gs has that screen treatment that repels oil making finger contact very resistive. It's horrible for gaming. The one I have specifically is the Power Support Anti-Glare Film. Highly recommended. Tried one from Elago and it's horrible.
The thing about CoD is that it's a LOT slower paced, so the slighty difficult controls are a lot easier to give a pass to. Maybe it's just me, but I can't play fast-paced FPS games on the iPod Touch as well as I'd like to...
Oh well u will get used to them play more and it will be better for u it will help u learn and get used to the controls