RVDT - Thank you for the reminder & update.
Now that the memory is jogged, you're right that a jet wash is not condoned, but
we tend to use it as a rapid / distant wetting method both pre wash & rinsing. Not to be used to blast the airframe (although muddy skids might get the high-pressure treatment), but to get things done quicker than just bucket or hose, as washing otherwise takes up too much operational time - we also have "putting-washing-kit-away-quickly-when-required" down to a "T"
Covers are, of course, a sensible precaution when parked cross-wind in damp / spray / salt environments but less useful when parked into wind, and also best not used when rapid deployment is part of the business.