Yep, I follow NutzAboutBolts' method for the gen3, which is to wash away. MyCarAngel has a youtube channel and uses a full blast stream (gen2 owners need to cover a couple of areas with foil).
I always spray my engine down with a light spray from the garden hose, then I hit it with simple green and a brush and then rinse. Never had an issue in 20 years and all my prius's the last 10+ years have been spotless under the hood. Just have to use some common sense!
