Clean Green is very good at removing greasy grime especially if you allow it to soak for a bit. But the only thing that concerns me from past experience is I found that odd metal bolt would develop corrosion later on - maybe totally unrelated to the Clean Green and mostly due to the car itself and its age.
But my cleaning process was much the same as above. I let the engine warm up so that the core was at least decently warm and then allow the exhaust and manifold a few minutes to return to more ambient temperature. I then lightly sprayed the engine with a GENTLE stream of water before applying Clean Green. Keep the water flow away from the delicate electrics and air intake - prevent Clean Green from getting into contact with belts etc. If necessary used an angled brush (kitchen or around the house type brush) to clean those harder to reach places.
Then thoroughly rinse the entire engine bay (minus the electrical bits) again with a gentle stream of water - I usually park the car such that the available Sun is shining into the engine bay to help keep some warmth in the engine bay.
I then start the engine and let it idle for a few minutes while checking that all electrical items are functioning - then close bonnet and take for a decent drive so that any moisture is "burnt" off completely.
Never had any problem with this careful approach to cleaning an engine - although with the extra amount of electronics in my 330i's engine bay I will just have to be that much more careful!
Philip