I do not know when the last time my ZJ's cooling system was serviced, so I got that accomplished the other day. It was running and maintaining close to 215*F when hot since I've had it. I took out the airbox to make access to the lower radiator hose easier for me. Just to show it. Looking up from underneath on the drivers side is the lower radiator hose attaching from the radiator to the waterpump housing. That is the hose I undid. I disconnected it from at the waterpump. All of the coolant just comes out at once. I used a rectangular tupperware catch-container to catch the coolant.
It is pretty easy. You just attach the lower radiator hose back onto the waterpump once the coolant drains. Then, fill it up at the radiator filler neck. I did all of this twice with the distilled H2O. I ran it in-between all of the refills for a couple of hours each day to get all of the old stuff out, and decently flushed system.

After I filled the overflow resevoir up to in-between the add & full marks, I started up the Jeep, and allowed the thermostat to open as it warmed up... with the radiator cap off. I filled the radiator up to the top at the filler neck, adding as it needed it. I shut it down. I let it cool off. I start it back up with the radiator cap off a second time. I check and refill both, at the resevoir, and at the radiator filler neck if needed.. It just needs a little extra coolant added usually on the second warm-up cycle, the second time after filling it.

This is about where the temperature stays now after done flushing out the cooling system with distilled H2O, and replacing the old stuff with a new 50/50 antifreeze & H2O mixture. The gauge needle was staying past the middle line prior to doing all of this. Now, it stays below the middle line with the new coolant. I put on a brand new radiator cap too.