Hi, Leslie.
You can definitely use CC on a manual treadmill. CC has steady state modes, hill climbs (you could do the incline for those, or just walk faster) and sprints (you could run on those). It's not so important WHAT you do (sprints vs. climbs, for example), but getting your heart rate into a specific zone, anywhere from 1 (warm-ups) to 4 (anaerobic).
I've used CC on a stabionary bike, on my reboudner, and while doing walk arobic type moves (with tall box climbs/overhead presses for the hill climbs).
Tomorrow is my cardio inteveral day, and I plan to do a CC. I'll proably combine my rebounder (for steady state and sprinte) and Transfirmer climbs (for hill climbs). Or whatever I feel like doing at the time!
I find teh music really motivating, and the workouts fun. I did wonder what I would look at when doing them, though, because I'm such a vidiot! But I ended up watching TV with the sound off and captions on (a Twilight Zone marathon last time) and that worked fine for me.