Whilst Santa came down the chimney with a pair of socks for me this Crimbo, my brother in-law faired somewhat better as the portly bearded chap left £188k of Aston DBS on his drive. Oh well - I suppose he did work bloody hard setting up his own business whilst I wasted money on scoobs...
Anyway, the point is that he has never taken a sponge to his previous cars and now, having splashed out a few quid at Halfords, thinks he can make a grand job of keeping it clean. Like most scoob owners, I am fairly fanatical at cleaning, but I wouldn't dare get near his wheels for fear of scratching something!
Would you advise him to get a professional valet in - that was my advice. If so, anyone good in Kent area so I can save his car before he gets a soapy bucket of Turtlewax and a gritty sponge out!

 

Let him go at the Aston with the gritty sponge, that'll teach him (eventually when he notices the nice swirl marks and dull paint finish).

If he hasn't got a scooby doo then I'd advise him to get a professional valeter/detailer in and give him a proper lesson on how to clean a car correctly.

It is amazing the amount of people as you say who clean their wheels, paintwork and glass with the same manky sponge. They don't think that the dirt/dust they removed from the wheels is then going to be used as a rubbing compound on their paintwork. They don't even both to rinse it out properly before grabbing some more foam from the bucket, let alone use lambs wool mitts and the two bucket method.

For what he has spent on his car then the amount he would pay a professional to show him how to clean it is peanuts in comparison.

 

Read up in the car care guide and advise him how to do it.
Different cloth/mitts/brushes for different bits of the car, two bucket method, hosepipe and loads of water.
My daughter bought a new Fiat 500 18 months ago, I'm the only one who has washed it and the paint is still immaculate - it's easy if you spend a bit of time on it.
Failing that for £50 I'll come and do it for him.