I have found its generally hard work. Does not seem to matter what product is actually use as the streaks come off when you wet wipe with a stiff brush or cloth.
Its the ground in streaks that are the problem, The streaks seem to be inbedded in the paint work its not the fresh streaks you have to worry about.
Chemicals I have used are TFR, Truck wash, there is another one I use it helps stop the buildup of algi.. but I cant remember that one just yet so will post later.
What do you use to clean a caravan a jet wash, WFP System other?
Dave