I just snow foam it, jet it off and then switch the jet wash water feed to a container of PURE water. You can buy it from fish shops for around 5p a litre and it’s sold as DIRO (de-ionised reverse osmosis). It’s what the window cleaners use and the aim is to jet off the tap water. If the tap water drys it leaves streaks, the DIRO drives without leaving a lark as there is nothing in it to get left behind. Stops those swirl marks.
