How do you stop a flywheel from turning while you torque the bolts?

 

There is a tool for that if you want to spend the money... google it. Flywheel wrench. OR just use a pry bar and get it in the starter head. yes you can do it with out busting stuff up.
What I do is use lock tight and hit the bolts with my 3/8 impact. Good to roll. But if you want to do it right try the pry bar or the wrench.

 

I was told I can use a long bolt through the clutch bolt hole and brace it on the block. Is that extra bad advice?

 

I just used to put a long, thick screw driver through one of the outer holes and locked it onto some part of the engine block. Ok, I had a second pair of hands those days. Or rather, my assistant had a pair of hands for me

Ok, so you've got a flexplate for a manual clutch.
I guess its similar there.

Edit:
Dammit! Mixed the words around. Sorry. Still... should be the same for both!