Here is a engine detail post I made while back when I owned TTRS. Main points are wash (spray with APC, agitate and rinse) not too much water light fan spray do not drown engine. Need to blow dry to avoid water spots IMHO or use CR Spotless or both. If you leave water and drive you will gets spots. Dress any areas you wish with dressing of choice. HydrO2 is nano protectant activated by water and is not required.
Washed underside of hood and engine with APC and rinsed. Sprayed underside of hood and engine bay with HydrO2 and rinsed with CR Spotless. Blow dry with Metro Blaster. Applied PERL to few areas. Quick easy way to protect under hood less than one hour start to finish.