To answer Desert Dweller question of why bother to wash your rig, knowing that the next trip will see it dirty again
Then I agree "Why Bother"

But...

For those of us who travel long distance/long time period

If we do not occasionally wash our rigs, we will probably end up with, potatoes growing out of the seams

On my first lap with car and caravan, I would clean my car at least once a week, (mainly roadwork/free camp, dust)

Very early in the morning, when the dew was on the car, I would clean it off with a dry chamois cloth, and keep wringing the chamois out, as it absorbed the moisture

It worked for me

I never tried this on my caravan, as I did not carry a ladder

I give my motorhome a wash prior to, and after, each trip
Unfortunately I am not a very experienced washing type person, which is my excuse for not washing it, while travelling