I had to replace the o-ring between the bottle and the valve on my Omega 74 cu ft bottle. Was instructed not to use any wrenches, just hand tight. That info came from Jim at Precision Airguns a long time ago. Sure do miss that place.
For what you are trying to do I would wrap the valve in a rubber strip and then apply force with a pair of vice grips. Should get you the torque you need without causing any damage.
For what you are looking to do I have to agree with the others. Hand tight on valve to bottle should be sufficient.