Quoting 89Mirageman:
I always use a pressure washer/purple stuff and only had one issue, that was when a little moisture got in the distributor cap. After wiping it out all was good again. Also I choose to do this when it's in the 90's here and leave the hood raised all day afterwards. I will say that the pressure blows nearly all of the oem decals off though. Like the ones on the radiator or wiring harness. Something I didn't really care about since they were daily drivers. Tom has the right idea if you're looking to preserve everything though.
Also this is just another way of doing the valvecover that I've found to be easier. Clean and polish the raised letters first. Then prime the VC and take a rag with a little thinner on it and wipe the primer off the letters carefully, then repeat the same procedure with the paint. After the VC has fully cured take a gray scotchbrite and go over them one last time. Doing it this way guarantees you don't nick the paint or anything. Not saying your way is wrong because I have done it that way many times. Just saying this is what I do now and it seems easier for me.
Yes, that's exactly why I like to do it by hand. I've pressure washed lots of engine bays, but I wanted to carefully go through everything and what this video doesn't show is that I was doing various maintenance work throughout the process as well. I'll be sure to post the maintenance video later, it's just not as interesting as the clean up/results in my opinion.
Thanks for the valve cover tip, that's another good method.