Mike,
I use a Backpack DIY System a bit like Chris mentioned. I love it and wouldn't use hoses out of a van but................
I notice you have a few large properties. The backpack would be a pain in the backside, filling it up several times. I only have 1 large property with, to me, endless rows of large pain windows. I only do the tops (a subidiotract for a local Contractor) but I have to fill up 4 times.
I would suggest you get a van mount or trailer mounted Tank with a delivery pump and pump controler and however much Microbore hose you might need (Hose comes in 50, 75 or 100 meter lengths). And put a 12v transferpump in the tank and get a backpack to do your domestics!! Because, mark my words, when you get the hang of WFP you'll want to wash EVERYTHING!!
David