Well apart from the obvious bucket and brush, there are one or two slightly more advanced systems you might consider. You have already mentioned the pressurised container, which is basically a garden or paint sprayer unit which you pressurise by hand. These only deliver realtively small amounts of fluid so good for getting the cleaning solution onto the roof, but not perhaps strong enough for rinsing off after brushing.
There used to be a car wash system that used 25L container and what looked remarkably like a caravan 12V submersible pump. If your only using it for rinsing water then there's no reason why you shouldn't use your normal Aqua roll and a spare caravan pump. This can deliver water to what ever type of fitting you like.
I have actually used a shureflow pump in a similar way for a different cleaning job., I just used a normal garden trigger handle and becasue teh pump had a built in pressure switch it just shut off when I released the hand trigger.