I have a pressure washer but it is never used on the caravan, so as others have suggested i have a through-flow extendable brush but use it without the hose attached - usually it leaks and easily disconnects and I don't like the free cold shower that ensues! I bought an almost rectangular bucket used with a dilution of my preferred product then dip the brush-head and wash a bit at at time, although a sponge to dip helps to remove any obstinate bits and also clean around the aerial etc.. I then rinse off with a hose on a sprinkler setting! I also put the caravan step inside, fully open the Heki and then reach out with the sponge to clean around the roof that is concealed from outside when the Heki is closed. Caravan paint is very thin so avoid any products that have any abrasive content. I like Mer for detailed cleaning of the front and back panels, that can be used neat as spot cleaner/polish or dilute for washing.