I often use an impact wrench. I have a Lifu splined shimano type tool, which looks like an impact quality tool, in my 1/2 drive pneumatic impact wrench. I've pulled a few threads out when I removed a 10 year old BB from my aluminum framed Giant, but I think that could have happened no matter how I turned the spline tool. Rusty BB in an Al frame can never be good. It has worked like a champ on the other frames I've used this technique on. Make sure you have the rotation correct.

Disclaimer: I am not a professional bike mechanic. I do my own wrenching.

Also, I've never touched a carbon frame. What are the fittings usually made of on a carbon frame? Aluminum? (by fittings, I'm talking about the BB shell, head tube, etc.)