Every hydrant manufacturer is different and it depends on how long the stem to the valve is. I was always taught at least 16 turns when you open a hydrant. I do know that the Water Department recommends that whenever you operate a hydrant to open it up as fast as you need to but to close it slowly. They also recommend that the hydrant should be fully opened when in use to reduce damage to the hydrant and the water mains.
Every hydrant is different. Some hydrants may only take 6 to 8 turns. I have seen some hydrants (Ludlow) take as many as 40 some turns. This was made this way to prevent water hammer. Also the hydrants in Chicago open by turning clockwise.
Caution you on some of the advice you have gotten. (Lefty loosey of course) is only in that person's district.
I suggest calling the water department, every hydrant is different to include number of turns, and which direction is open verse close.
New standards: If you live in the cold, where the hydrants self drain when fully closed, EPA now requires wet barrell only, (non-self draining and manual pump dry to prevent freezing) this is to lessen the chance of cross contamination of the public's drinking water. So in future upgrades or new installations, you will have a mix of self draining and fully wet that need additional maintenance to keep them in service.
If you live in the cold, where the hydrants self drain when fully closed, EPA now requires wet barrell only, (non-self draining and manual pump dry to prevent freezing)
How does one go about draining a wet barrel hydrant? We don't have any here, but I'm under the impression the valve is right at the discharge making it impossible to put a suction pump in one, and even if you could there's gonna be constant water in the hydrant unless you shut down the valve to the hydrant on the main?
Or are you saying the dry barrel hydrant without a self drain that has to be pumped out?