Im with Troy Sherer - "I aint scared of no wires"...
It it was me, it would be Meguiars Super Degreaser, sprayed over entire compartment, under hood, not on any hood insulation, fenderwells, everything, let it sit for a few mins and then pressure wash it all off...
An amazing amount of dirt and grease will come off easily.. This product is low foaming and rinses off really well..
Just because its a pressure washer doesnt mean you have to hold it right up against the parts... You can hold it farther back and still get good results, experiment with this...
I have never hurt an engine, compartment, wiring, anything, doing it this way, for decades...
Of course old school engines, need to put a plastic bag or something over the air cleaner and try to fit something over the distributor as best you can..
Worst thing that can happen - you get some condensation in the inside of the distributor cap and have to pop the 2 holders out, lift it up and wipe it dry with a towel and it will be fine...
If the engine is overnight cool to begin with, there is less chance of getting any condensation under the cap..
All Ford engines were notorious for getting wet under the cap - Chevrolet, not so much, but if it doesnt start up, I would look there first...
All engines get wet in the rain under the hood from water coming in through the radiator and from underneath and through the openings below the fenderwells...
I would also do it and then leave the hood open while you wash off the rest of the car, then come back and blow out the entire compartment, especially the engine as best you can, and then start it up and let it dry some places you cant get to ....
A little ride down the freeway will also help if you think you need it..
Good luck !
Dan F