All of the ideas put forward in their context so far have good merit.
Actually for my drive car, which remains out in the weather all of the time, I have used a different approach altogether to keep it clean.
Now retired, I detailed new cars for delivery for about 8 years.
I still have access to a water blaster. Essential to remove most dirt from paint and in the wheel arches, where rust quite often appears first. Standing instructions for Army vehicles is to water blast them at every opportinity to remove mud, because it will lead to a shorter chassis life if it is not removed.
Same applies the wheel arches in domestic vehicles.
Sometimes, when road grime builds up on the lower exterior painted panels of a car, water blasting will not remove all of it. In this case, I use a lean mixture of shapoo and a clean sponge. For the rest of the car I just use plain clean water and a sponge, then blast again.
I clay block all of the exterior paint while it is still wet, give it a quick blast again, then chamois.
I haven't used polish for about three years now, but apply a paint sealant that is not sold domestically. There is a guarantee that is supposed to last for a year, but I think that claim is garbage. I use paint sealant three times a year: just before summer, 2 to 3 months after that, then during winter sometime. If the car is always garaged, then perhaps the year long guarantee may be OK.
If I want a really top class shine over the paint sealant, I use a creme canuba wax. Only my 6.9 receives THAT treatment.
I would image that if the car is always garaged and polish is used only, without the paint sealant, to maintain a top shine, then polish would have to be applied every 3 or 4 months. My drive car, if it is lucky, will get polished once a year, just before summer.
If the car gets dirty between applications of paint sealant , I just water blast it. Almost all dirt, because it cannot stick to the paint, just flies off, leaving a perfectly clean paint surface. Such an approach without the use of any shampoo, extends the life of the paint sealant. I just lightly trail a chamois over the paint, then straight back onto the road. Such a quick clean job takes only 5 minutes or so.
Even when my drive car is dirty, water always forms in large beads on the paint during rain, as if it has just been polished. I would believe that the paint sealant that I use will considerably extend the life of the clear topcoat. The car is now 13 years old, and the topcoat shows no signs of deterioration at all.
Water blasting the tyres prepares them nicely for the application of tyre shine. I never use this stuff anywhere on any of my cars. Yuch!
I use a two horse power industrial vacuum cleaner the extract all dirt from the boot and interior of the car. This mean machine can be rather noisy to use, as you may well imagine. Both the water blaster and vacuum cleaner are noisy enough for the use of ear muffs.
I DO NOT use the water blaster in the engine bay of my 6.9; it is just too powerful. A low power domestic blaster with the power turned way down, with a trace of non alkaline degreaser added to the jet, is a much kinder way to go. That will get into all of the hard to reach places in the 6.9 engine bay.