Using the engine torque to remove the harmonic balance bolt is probably not the safest idea.
Use an air wrench.
There are torque specs for the harmonic balance. Off the top of my head I think it should be torqued to around 70 ft/lbs, then loosen the bolt half a turn, and retorque to approx. 38 ft/lbs.
You may need a bolt that is longer than the stock bolt to seat the harmonic balance on the driveshaft because often the harmonic balance won't fully seat. If it won't seat on the driveshaft, you won't be able to thread the stock bolt. Use the longer bolt to seat it, but be careful not to over tighten it. Remove the longer bolt, and then torque the stock bolt to the proper specs.
At those specs, you shouldn't be able to turn the motor over if you place the transmission in 3rd or 4th gear. You don't have to gorilla wrench your harmonic balance on. I'm not sure about AT cars. If your engine is still turning over, maybe remove a spark plug and jam one of your cylinders up with a long screwdriver.
(Don't really do that...)
I got this information from Steeda when installing UD pulleys, but don't quote me on the ft/lb specs...they may be slightly off.