so what do you use then Yada?
I use a very large van mounted pressure washer set up, running at 41LPM - it allows rapid cleaning, negates the need for chemicals in most instances, will remove chewing gum with cold water @ about 30 LPM because of correct nozzle choice.
Combined with a van mounted chemical system - set up in the last couple of weeks that will draw water from the main tank and then from a drum of chemical & then a drum of fragrance if needed.
Occasionally I will use an environmentally friendly degreaser - sourced for some work @ Highways England, South Mimms depot a good while back but it was more the challenge of setting the system up & if I want to use something like hypo/chemical moving forward I don't need to get a backpack out or mess around flushing a pure water system out - it can just be switched on, 100 metres of hose pulled out, apply & then packed away.
I see a use for much more damaging chemicals than hypo but with this set up they can be controlled much easier with less handling.
There is also a separate tank for WFP window cleaning.
This has a bank of 3 x 110 amp batteries topped up with a solar panel set up, powered by 2 x 120 watt panels fixed to the roof.
It is as near to completely self sufficient a set up as is possible (I believe), nothing needs putting into the vehicle or taking out, all parts work together.
I'm equipped with the gear to clean volume because I made the mistakes in the past of not being.
If you're at the other end of the country from where you are based and you aren't equipped you don't let it happen again.
I don't knock anyone who wants to hypo everything - if it works for you go for it but it isn't always as straightforward as that.