From the Engine Cooling manual:
IMPORTANT: Draining the cooling system with the pressure cap installed will siphon the coolant from the overflow tank.
(I think this is important to know, it could tell you if the hose between the radiator and the overflow tank is clogged or not or if there is a pressure issue. This will allow you to clean it, also.)
Draining Procedure
1. Park vehicle on a level surface.
2. Allow engine to cool.
3. Remove the radiator cap.
4. Raise and support the vehicle.
5. Place a drain pan under the lower radiator hose connection at the bottom of the radiator.
6. Using J 38185 slide the hose clamp back on the hose. (J 38185 is a stupidly-overpriced tool, just find something that can loosen the clamp)
7. Slowly remove the lower radiator hose and drain the coolant into the drain pan.
8. Inspect the engine coolant for the following conditions:
--Discolored appearance - Follow the flush procedure
--Normal appearance - Follow the filling procedure
--If a complete block drain is required, remove the plug located on the LH side of the block. (This is telling us there's a plug, but in the flush procedure there's no mention of such a plug, just the thermostat)
Flushing Procedure:
1. Drain the cooling system (already did that up there ^^)
2. Remove the coolant recovery reservoir.
3. Clean and flush the coolant recovery reservoir with clean, drinkable water. (Could use some distilled water if you're paranoid)
4. Install the coolant recovery reservoir.
5. Remove the thermostat. (Note that if the thermostat is a permanent part of the housing, you'll have to reinstall it for running the fill and run procedures. If it can come out of the housing [the metal tube], I believe it is suggesting that, so water is circulated from the get-go)
6. Follow the drain and fill procedure using only clean, drinkable water.
7. Run the engine for 20 minutes.
8. Stop the engine.
9. Drain the cooling system after allowing to cool.
10. Repeat as necessary until the fluid is nearly colorless.
11. Install the thermostat.
12. Fill the cooling system.
Filling Procedure
1. If a complete block drain was required, install the plug.
2. Install the lower radiator hose.
3. Using J 38185 slide the clamp to the original position (use what you used before again, don't bother getting this overpriced tool)
4. Lower the vehicle.
IMPORTANT: Slowly add a mixture of 50/50 DEXCOOL antifreeze and deionized water to the cooling system through the top of the radiator until full. Refer to Capacities - Approximate Fluid in General Information. (According to owner's manual, SWB w/ I6 is 10.8 quarts and LWB is 13.8 quarts.)
5. Remove coolant recovery reservoir cap.
6. Fill the coolant reservoir with the remaining coolant.
7. Install the coolant reservoir cap.
8. Install the radiator cap.
9. Start the engine.
10. Run the engine at 2000-2500 RPM until the engine reaches normal operating temperature.
11. Allow the engine to idle for 3 minutes.
12. Shut the engine off.
13. Allow engine to cool.
14. Top off the coolant recovery reservoir as necessary.
15. Rinse away any excess coolant from the engine and engine compartment.
16. Inspect the cooling system for leaks.
17. Inspect the coolant concentration using J 26568 (another overpriced tool, just get a coolant tester).