How to seal new CO2 valve stem

[modelafish]

I just replaced the valve stem that connects the CO2 tank with the regulator. What is the best way to seal the threaded connection into the regulator? I have pipe dope and teflon tape. What is recommended ?
Thanks

 

[day_trippr]

Properly applied either will work, some of my regs are taped the others are doped...

Cheers!