How do you remove the boiler drain from a hot water heater to clean lime out of it?

How do you remove the boiler drain from a hot water heater to clean lime out of it?
A boiler drain has pipe threads. Simply unscrew it counterclockwise. Be sure the power's off before you drain it. You might try pouring Lime Away or CLR in to soften the buildup before you attempt to flush the minerals that have built up. Good luck, Tom

Why are you removing the drain rather than just opening it? Is your build up so extensive that it is blocking the valve?