When I got my Insight the engine bay was a mess. I soaked everything that wasn't attached to an electrical connection with a decent citrus engine cleaner. Let it soak in for a while (the engine was already hot) and then hosed it off. Did that a few times and then got in there with a scrub brush and got what I could with that. The rest I cleaned by hand and detailed with rags, toothbrushes etc. The engine compartment now looks like new.
Heck, I even got a trophy at a car show with it - yes there were other cars in my class.
