There are simliar things between driver and car. One of these things is, that both are ready for a shower after a couple of days or weeks – depends on the olfaction. And of course how dirty everythings gets through the time. A garage queen do not need to be washed once a week.
But what about a filthy car? Depends what kind of dirt you have on it. Is it just dust? Then it isn´t such a problem. Just blow it with high-presure washer away. That should be fine.
Is it more and is it crusted than you need more then a bit of water.
But is it good for the paint to be maltreted be brushs and high-presure water and some chemical stuff to get it shine? I am not sure. Some thing are necessary to get the crust away – but not all tools are right for this.
Look for a washing company with a “mild washing street” or a “paint protection washing street”. That should be the first “must” to be sure that your paint is not maltreated.
Only use chemical stuff you´re sure about, that this will not destroy anything on your paint.
I prefer to clean the car with the high presure washer and then with some cleaning soap for cars and then clean the car with fresh water – finished.