I always used Simple Green - it's not so caustic like some products so it will likely not damage things - mist the area with a little water, then spray SG full strength and give it 10-20 min for it to work. Then rinse it with a stream of water but don't get it into the engine intake and if a gasser, avoid the ignition components. But you probably know that...
I used this method on my 91 300D 2.5T and the engine compartment is pristine. Do it when you notice grease building up and it'll stay clean.
Good luck,
LarryT
91 300D
74 911
06 E350 (Possibly scrap)
06 Ford Explorer 4.0
66 MGB