I spray degreaser first on all the engine parts I want cleaned, and then I use a steam cleaner to rinse it off. I've been doing this for the last 10 years. The hot steam helps the degreaser clean, and then it evaporates. I even clean electrical connections. The steam gets all the gunk off and then takes a few minutes to dry. No damage done. This way does take longer compared to using a garden hose/pressure washer. But I think it's safer.
Something like this:
When I first bought mine over 10 years ago, it was around $150. Now I found it for like $30 on Amazon
http://www.amazon.com/Electric-Differen ... held+steam 