Smuj
In the late 60s there was a 'dedicated' wash team of sorts: a corporal rigger was i/c a couple of civvies and these were occasionally boosted by some casual RAF 'volunteers'. The team wash system was introduced while I was on Blue Team in the very late 60s, quite an enjoyable diversion for us hangar-bound techies in the summer, but not a totally enjoyable experience in the cooler seasons!
I heard about the 'aertex' Herc from 70 but, like yourself, didn't know how/why/what happened to it.