Hilary,

In between car washes, I just squirt the windscreen washers and use a pot
scourer if the bugs begin to bug me.

When I get the car serviced they wash & valet it then, without extra charge
(yes I know I pay for it, but I don't get it cheaper if I decline ....) so I
make sure it is filthy before the service :-)

You're not, by any chance, the sort who would have a cleaner in the house
but would then stay up half the night getting the house straight for the
cleaner in the morning?

Dave