No a pressure washer is a good thing to use. Just try to avoid soaking your engine. Engines are not really meant to get wet or soaked for that matter.
Today I pressure washed my under body and I made sure is was completely dry and clean. I then got about 10 cans of High Gloss Black Rustoleum Industrial Grade Metal Spray Paint and I spray painted the frame, driveshaft, diff, rear axle, and any other places that were painted black from the factory.
The shine looks insane!!! I then let it dry for about 5 hours and then took it to class and it now looks like crap... but it I know it won't rust, corrode, and it will wash off really easily. Not to mention the insane shine with no need of tire shine!!!
I totally forgot to take pictures... but next time I wash it I'll take some pictures. It still looks insane even after some sand and dirty water got on it.