They have a retaining nut, like any other hub, but there is no "special tool and drain the grease out of the hub in order to remove the drum". Just a large socket/wrench, snap ring pliers and it slides off the spindle. It is pressed into the drum (or disc) hub, but you don't press out unless you need to replace the bearing. The grease is sealed in the bearing set and has no "draining" nor repacking provision.
"If the women don't find you handsome, they should at least find you handy." - Red Green