If you use the Prestone method, you will not get a complete reverse flush of the engine block because the thermostat has not been removed and will not allow a reverse flow from the outlet of the intake manifold backwards through the heads and block. You will also not get a reverse flush of the heater core because the water is flowing through the Tee to the heater core in the normal direction of flow. And, the only part of the radiator that is reversed flushed with the Prestone Tee method is the right side tank. The Prestone method will remove most of the coolant from the engine but the area near the thermostat becomes an area of no-flow. When I use the Prestone Tee to flush, I do not cut the heater hose to install it, but simply remove the hose from the engine, insert the tee, and add a short piece of hose to connect the other side of the tee back to the engine. That way, the flushing tee can be removed and the hose replaced without adding two more fittings that can become a leak.
Depending on how much time you have and how meticulous you care to be, you can reverse flush the heater core, engine, and radiator, by removing the thermostat, isolating each part of the system and flushing each part backwards with a garden hose. Remember that the design operating pressure of the cooling system is about 17 psi and most city water pressures run at about 90 psi. You can damage your heater core, or radiator with 90 pounds of pressure. Minimize that possibility by making sure during flushing that the other end of the portion of the system you are flushing is open, and that the hose nozzle is only held in place by hand or sealed with a rag in the larger openings like the radiator hoses. That prevents the development of damaging pressures.
To reverse flush, you simply go in the opposite direction from normal flow. Normal flow is: From the bottom of the radiator into the water pump. From the water pump to the engine block - from the block to the cylinder heads - from the heads to the intake manifold - from the intake manifold to the heater core - from the heater core to the water pump. From the intake manifold past the thermostat to the upper radiator hose - through the radiator left to right and top to bottom.
One way to reverse flush each component is described here: http://www.bonnevilleclub.com/forum/...ic.php?t=84203
When you are done flushing, you will want to fill with "mixes with any color or type" coolant using the method described in Techinfo: http://www.bonnevilleclub.com/forum/...=article&k=100