Similar but slightly different to above. Soft bristle brush with extendable long handle but don't bother connecting it to the hose. I give the whole van a quick hose down before starting then mix up a solution of Fenwicks in a bucket and using a plastic jug liberally throw some of the solution over the roof and leave to soak for a couple of minutes. Not nearly so neat and precise as Parksy but still works. Then get the brush going followed by a rinse off. Generally use stepladders at the side of the van, but can reach some parts of the roof from inside the van via roof Windows and smaller set of steps. I've read of some folk using ladders propped against the top edge of van padded with towels to prevent damage. Did try it once a long while go with no apparent ill effect on the van but didn't feel comfortable doing this although it did make access to the roof a lot easier than the step ladders because of the uneven ground surface around my van. Remember, safety first when up any ladder, better a grubby caravan than a broken head.