You could try 'Stardrops' all purpose household cleaner. Alternatively, you could purchase some 'Fenwicks' which should cleaner the exterior of the van with little effort.
It is a paste that you apply with a damp cloth, then buff to a shine.
My next door neighbour decided to spray his fence with *uprinol fence spray, the next day I found overspray on the side of my van,as the sray was water based I tried Silky which removed the problem without damaging the paintwork of the van.
Wash with stardrops remove any black marks with Mr Sheen furniture polish, its so easy you wont believe it. About 15 or more years ago I was having difficulty pulling an awning through so I used some Mr Sheen as a lubricant, the black marks that refused to go with whatever I used went with a simple rub with a cloth, used it ever since.