If it's a fiber gear you don't want to re-use it anyway. Those are wear items, like belts, and it's pointless to re-use 'em except in Very low mile situations.

So, if you're anywhere near as lazy as I am, you can just block the motor rather than holding the cam gear. Obviously you don't jam the teeth of the gears themselves. If you haven't got a flywheel stop tool, just stick the car in 4th, chock the wheels, brakes on, long cheater bar, you'll get it done.

Since you're already replacing the gear, don't worry about torquing against it. Have at. The gear to be careful with is the new one. And, that new gear will survive one careful torquing on installation. Really, it's okay.

I would agree that a standard handheld torque wrench is the safest way to tighten the new gear: nobody ever broke the cam nose off when they carefully did it by hand. The standard torque applied slowly by hand will do No Damage Whatsoever to the gear teeth, despite how scary it may seem.