What I usually do is to flush the engine with clean water and then drain. I them add one gallon of concentrate and top off with a 50/50 mix. You could punch out a freeze plug in the block but that is overkill.
I was working on the cooling system and noticed that the duratec seems to be different from many other engines. It seems the coolant inlet and outlet are next to each other on the tranmsission side, on a high part of the engine, so I think it is not easy to get water out of the block itself. Don't know how much coolant stays in the block, though. Maybe a lot of it is in the heater lines.
The Duratec, like many modern engines, has reverse coolant flow. Coolant flows thru the head first, and then thru the block unlike older engines that flow coolant thru the block first and then thru the head. That is why the hose routing seems kind of weird compared to older design engines.