It's actually not that difficult to do a really good job once you know what you are doing and have all the right products and equipment.
One part of the secret is that you have to keep at it constantly rather than doing one big clean a year and a whole bunch of quick washes along the way.
It's a big topic, so briefly this is what I use:
HIGH PRESSURE CLEANER- I use a top end Karcher; but there are lots of different ones around that will work just fine. There is no problem using them in the engine bay or on the paint PROVIDING you use some common sense. Don't spray electrical connections or computers. Don't place the nozzle mm's away from the paint surface. Especially be careful using one on 3M stone chip film as it WILL tear a hole in it if you get too close to the surface.
I mostly use the pressure cleaner inside the wheel wells/wheels and underneath the car. Once or twice a year i remove the wheels and clean the suspension properly- normally after a Tassie tour of a couple of thousand km's. the rest of the time using the high pressure cleaner with wheels in situ does the job just fine. Hot tip- get yourself a long handled dish mop from the kitchen and use it to get inside the wheels while they are on the car. you should be able to clean the inner surface right the way around and also do the brake callipers on all sides with it.
CT33 Truck cleaner. Fantastic and safe product if used correctly. I never use it on paintwork; but use it in different dilutions for different applications. Inside the wheels and wheel wells and underneath the car is about a 10% dilution with water. In the engine bay it's weaker again. I have never had a problem with it stripping the finish or gloss off anything in probably 20 years of usage.
ENGINE DEGREASER- Be careful with these as some of them are strong enough to stain surfaces. Find one that works and stick to it.
PLEXUS SPRAY- Use this on the 3M stone chip film to keep it shiny and reflective. Probably once a month is best; but no longer than 3 months on a daily driver. It is also a really good product to provide some shine on all the rubber and bits and bobs in the engine bay too. Spray on and buff off.
ARMOUR ALL- Be a bit careful as it's very oily, overly glossy and attracts dust like nothing else. I pretty much only use it on tyres myself.
WINDEX- I use this to clean all the glass.
LEATHER CLEANERS- I tend to use products that are used to clean motorcycle leathers. I then use hide foods of various descriptions; but don't really have a preference. Experiment and see what works for you.
CLAY BAR- No preference; but I use these to prepare the paint surface before I start with the polishing phase.
ORBITAL POLISHERS- I like the Rupes "Big foot" orbital polishers.https://www.youtube.com/watch?v=qo8eP-OfEAchttps://www.youtube.com/watch?v=7cAnevFwZeY
WAX- I think these come down to personal choice. There are lots of good ones out there, just experiment.