Disconnect the two hoses from the heat sink. Push the end of the garden hose into the top radiator connection short tube and seal with a rag.
Reinstall the radiator pressure cap and fill the water. Rinse until the water is flowing.
Check by trapping some water in a glass jar and checking the deposits that can only be seen in still water.
Flush the water through until it runs out clear.
If the water does not clear within a few minutes, flush the radiator back. Seal the hose into the bottom short tube. Attach a long plastic bag to the bottom with a hole to the top stub to direct coolant away from the engine and electrical components. Rinse until the water is flowing.
Reverse flushing a radiator
If simple reverse flusing does not clear the radiator, take it out of the car.
Prop it upside down and seal the garden hose into the bottom stub, which is now at the top. Flush hard until the water runs out clear.