Whenever I need to work on something that gets coolant through it (heater core, radiator, water pump, cylinder head, exhaust manifold and turbocharger (if water-cooled)), I always flush the system with clean water to remove all traces (well, 99+%) from the system.
This way there is only water on the garage floor and it's not as slippery as coolant and there isn't any coolant to get on your hands, tools, interior of the car, house, etc. If you're disassembling the engine--like pulling the cylinder head--only water droplets can get into the oil passages instead of coolant. With just water, you can run the engine for 10 minutes after it gets hot (oil temperature greater than 220 degrees F) and any water will evaporate. If this was coolant, plan on changing the oil a couple of times to get it all out.
SAFETY NOTE: Coolant is extremely poisonous! Just a few drops will kill a 50-pound dog so keep it covered, hidden, and clean up all spills immediately. Don't let the neighborhood kids play in it either. DO NOT flush high concentrations of coolant into the street--it's illegal. Store all waste coolant in plastic bottles (like the same bottle the new coolant comes in) and dispose of it properly.
It doesn't take much thought to see the benefits of not having coolant on the interior carpets, etc. when changing the heater core either. I use a 1/2-inch garden hose with the metal threaded end cut off--also use this to wash the cars. With the end cut off you can't scratch the paint! Anyway the outside size of a 1/2-inch garden hose happens to be 1/2>-inch and the inside size of the heater hose that comes out of the thermostat housing also happens to be 1/2-inch. I think Ford designed it this way just for me!
To change and flush the coolant, or just remove and save it so you can service the car, let it cool (fewer burns) and place a drain pan under the radiator petcock. Open the petcock and start the draining. Slowly open the radiator cap--drain flow will increase--and be careful to not overflow the drain pan (still gotta move it and pour into some container). This empties the radiator only.
Disconnect the hose that attaches to the thermostat outlet bypass - same place the upper radiator hose connects but it points to the upper-right side near the exhaust manifold. If you have a water-cooled turbocharger with the factory tubes, this hose will connect to a black 1/2-inch steel tube that runs alongside the cam cover. If you have an early SVO without the water-cooled turbo unit, the tube is silver in color (bright cadmium plating) and crosses over the AC adjuster bracket and continues rearward under the exhaust manifold. Disconnect the hose end that attaches to the thermostat housing. Plug the thermostat housing that the hose came off of--I use an appropriately-sized cork plug from the hardware store. Now all the garden hose flow will come out the radiator cap and drain cock holes. You might want to use some sort of deflector tube to keep all the coolant/water flow from covering the battery and tray near the radiator cap exit/entry point.
Then plug the garden hose into the open end of the coolant hose and slowly bring the water flow from the garden hose. This action will push the coolant from the block to the radiator through the lower radiator hose--so be prepared to catch more coolant draining from the radiator. If you want to save the coolant (since it's really good for several years and doesn't need to be replaced just cause the water pump is being replaced) watch the stuff coming out of the radiator drain and stop the catching when it changes color.
To re-use the coolant, just filter it when you put it back in--a large coffee filter inside a large funnel works just great--and measure it's specific gravity and add fresh 100% coolant to get it between 50 and 70% content. All parts stores sell coolant testers--they're about $5.00; so get one.
OK, back to the engine. If you want to completely drain the block, there are two drain plugs on the block--one is just above the starter motor and, if you have the factory tubing for the water-cooled turbocharger, a nipple is threaded into the block in the drain plug hole. It's easiest to just pull off that hose and let it drain there. If you have an earlier SVO without the water-cooled stuff then just unthread the plug in the block. Remember to flush with water first so you don't get that gummy coolant into your new starter motor either.
There is another drain plug in the block at the opposite corner--under or near the power steering pump bracket depending on what year and which bracket you have installed. By far, the exhaust side one is easier to locate.
Just reverse the order of disassembly and fill with coolant again. Keep the thermostat bypass hose disconnected until coolant just starts to appear at the thermostat outlet when filling at the radiator cap inlet then install the bypass hose end. This helps fill the cylinder head and removes the large air pocket. Now start the engine and let it get hot enough to pressurize the system. Make sure the overflow bottle has enough coolant in it before the engine cools and it will draw in the coolant to displace any trapped--and discharged--air pockets.
Happy motoring!