D6 Radiator

I have a D6 that, I need to drain the radiator on. The drain mechanism seems to be froze up. Any recommendation on how to get the mechanism unfrozen. Will I have to remove the mechanism to do this. Are is there a special way to turn the mechanism or is there a special tool to turn it with. I'm a new bee at this stuff, kind of walking around in the dark. Thanks Shortorder.

The normal drain plug takes a 9/16 in. socket I believe. Standard bolt rotation to open and close. It's a pretty stout assembly so I think you can crank on it pretty good if you have to. The valve itself is stainless steel and can be removed. If all fails you can drain by disconnecting the lower hose which will drain most but not all or......unbolt the three cap screws from the bottom tank and remove the whole assembly.