Sounds like a nurse giving a sponge bathI won't use a pressure washer. Don't really even like the garden hose idea. Too many issues in the past. The degreasers are nice and get things clean, but they're almost never good for plastics and even rubber. Simple green used to be my go-to for cleaning in the engine bay, but no more.
So, what I use is nice warm water from the house. 2 pails. 1 has warmer water with a good bit of dawn dish washing liquid. The 2nd is just warm water. I select the area that I'm going to work on, carefully use a microfiber cloth dipped in the warmer water with the dawn. Wring it out good, and then individually clean an area. If it drips, I'm using too much. The first wipe should get grease and dirt loose. Then I use a 2nd wipe with the plain water and it gets anything remaining off. I know it sounds like 100X overkill, but since I switched to this method I have had zero issues and everything is actually much cleaner than the results I used to get. If I do a full wipedown it takes me about 2 hours.
I'm not knocking others who have success with chemicals and pressure washers, YMMV.
Pressure washers have a high propensity for forcing water into your distributor and spark plug connections. This means you won't be firing efficiently on some plugs which results in the engine missing and running roughly.
Two alternatives: 1. Waterproof your wiring system like you would do for crossing deep creeks. 2. Cover your wiring with a baggy.
I prefer number 1 because covering anything with a baggy will prevent you from getting that part clean.