Best way to wash the engine:
This is my eclectic - in and out of order - thoughts. So just rearrange it in the right sequence in your own mind.
I've done this a lot. Here's the method that works best for me - although others probably wouldn't bother to this extreme, it means I get a great looking job - and don't have to do it near as often.
First, I do it at home. It's easier than getting tiny bits of grease all over yourself at one of those carwash places, then having to drive home, getting it on the upholstery. There's also the problem of how do you get home if the car won't start afterwards from all the moisture.
I cover the alternator and distributor with a thick cotton rag - like an old towel to cover any sharp bits - then two plastic bags over that (because you be certain one still always rips). Then another rag so the jet from the hose doesn't rip the plastic. And unless you're planning to be real careful, tie it somehow with string/rope/occy strap to stop it coming off. (Be careful of occy straps too - I saw a guy nearly lose his eye once!) You can clean these two later by spraying degreaser onto a rag and wiping.
You could also remove the sparkplug leads, because water will run along them to the distributor. But I don't bother. I did it once and the car still didn't start any easier - and I only get the order mixed up putting them back on. I have other ways around the car not starting afterwards, so I don't bother removing the leads now. I do pull them off one at a time later, spray degreaser on a rag, and wipe them clean.
Ok, now - drops of degreaser WILL mark the paint. So unless you want to spend a LONG time polishing those marks off later (much more than a general wash and polish - believe me) - I would also cover the side guards with plastic, and the windscreen, maybe even some of the roof. (You can get large sheets of plastic from electrical stores - from them delivering whitegoods. Ask them if you can have some out of their skip bin - because a store near me has no problem with giving it to you - but they have to get it for you themselves, because of ridiculous liablity insurance).
I would also get someone with a second hose if possible - or a sprinkler - or keep interrupting yourself from doing the engine - to keep the car paint continuously wet. On a shower setting on the hose fitting - so any stray drops of degreaser or grease run straight off.
Then a spray bottle and degreaser. Or spray cans. Lots of degreasers mark metal - such as large piece of shiny metal where your throttle is mounted. ;-p So if this bothers you, try and find one that says it's safe to use on metal. (I can never find one.)
Also a 1-inch paint brush, a toothbrush, some rags... And a plastic hose nozzle from Bunnings, with a small hole about the size of the lead inside a typical wooden pencil.
Degreaser is often highly irritating to the skin, but I don't wear gloves. They're too clumsy to clean in. Degreaser gets into every crack of your skin and itches and burns, but I just put up with it - don't scratch - because it makes tiny scratches in your skin which makes the burning worse.
Oh - and old clothes obviously - and park the car where it can sit to dry out afterwards without blocking other cars/people if it won't start.
I have bad hands. So I have to hold the head of the brushes, spray the degreaser on, and 'rub through' the grease until I get down to whatever the surface is beneath.
It's nearly impossible to get spray bottles - that aren't competely full - to work upside down. So I try to do all the 'upwards/undeneath' stuff first.
In spite of the water protection for the alternator and distributor, the car/s rarely starts afterwards. And I can't be bothered covering all the eletrical. I've found a way that works, and I just stick to that.
First I wait for a hot day. With the heat (which is good later for drying out the engine), the burning skin from the degreaser - I don't mind getting soaked. You get to hose the kids or wife inbetween too.
I soak everything in sight with the spray bottle, to start working on the grease. Then I start high up in the engine, spray again and brush everything as I go, down to the surface, to be sure I got through the grease. Where you've already done, keep it wet with degreaser. Because once it dries the grease dries on again too - and although it comes off easier the second time, it will need to be rubbed yet again to remove grease 'spots'. I guess you could do a small section, hose it off, then degrease the next section instead. But I've found it's easier just to keep going and using degreaser to keep everything damp. Because by the time I get to the bottom, all that extra degreaser has made the worst stuff (which is always lower down) soft and ease to remove.
Whichever way you do it - with water or degreaser - keep everything damp. Because even if you degrease one section at a time, then hose off - stray drops from doing the next section will settle where you've already done. In other words, even the place you already cleaned - I wet it down again to stop it drying - until the final hose off, when all grease is washed away and can't redry and stain again.
Pay more attention to undernearth surfaces - what you can't see - than what you can. Or you will run out of degreaser doing the same areas you have several times, and will always miss the worst of it. I've lost count how many times I thought I was done, only to wash down, stick my hand in, and have it come out covered in black streaks.
I do underneath the bonnet and all the paintwork too - with the paintbrush. Because of my bad hands, I mostly have to hold the brush at its head and kind of rub the bristles back and forth through the grease - rather than 'paint' at the grease.
Oh, and if you're concerned about the metal of the brush scratching things, tape it with masking tape first while it's dry. Painters tape might also work - but because that comes off more easily, it may not stay put with all the moisture. That's something I'll have to try now I have some painters tape lying around.
I've found this way gets them the most clean, and means I don't have to do it as often, and is a lot easier next time. But my car/s rarely start after doing this. So when I think I've got all the grease, I hose with the blast nozzle - everything - just try to do it in a downwards direction near any electricals of course, and don't for example, sit there directly drowning the computer with the hose.
I'm making it sound like I'm more careful than I am. But as I said, my cars rarely start immediately after - so I just blast everything with water.
Now it's mostly clean - I check for anything still with grease. Do anything I find again - hose entire engine bay down again to get any spots. Then I hose down the whole car to be sure no degreaser or grease is on the paint. (Which either someone else, or me, has been keeping wet too that entire time.)
Most of the engine I just allow to air dry. But I remove the rags and plastic bags from the alternator and distributor, wipe them with degreaser sprayed onto a rag, clean the leads with degreaser on a rag, remove the distributor cap, soak up any water inside the cap, or that is sitting in depressions around the motor with dry rags.
If it's a really hot day, I leave it to dry for a couple of hours with the hood up. If it's not that hot (and sometime still when it is), I put an old fan heater in there - on low heat - not really close to anything, and wedged so it can't move and melt anything - and I lower the hood for a couple of hours.
I wouldn't recommend starting the engine at least for a couple of hours - but I do sometimes. The car usually starts with a cough and shake, but a short drive soon dries out the rest. Keep in mind if there is unseen water in there and you start it straight away, the fan will probably flick water up onto the underside of the hood you just cleaned. Or you could just play it safe and wait until the next day - then wash the body - and garage it.
