That owner's manual recommendation has been around for a long time and
it works.  The C5 manual also suggested using household glass cleaners
(Glass Plus, Windex, etc.)  I'm not fond of Windex since it leaves a
haze.  I've got a 'car-nut' neighbor who swears by newspaper but that
leaves a film of printing ink.

I'd avoid Carnuba because you want clean, not wax build-up.  I've been
using a gauze pad and aircraft windscreen cleaner (another, "apply-let
dry-remove" product) on my C4 'glass' top and am still pleased; however,
17 years my not be the 'long term' you're looking for (:-).  The
'powdery' residue is fine enough to not scratch.  (The C5 manual says,
no abrasives--which would include most paste and liquid car polishes.)

Years ago, Gold Seal made a great product called 'Glass-Wax' which was
removed dry.  Good stuff but the EPA killed it--probably contained
naptha.  I think you'll do OK with the GM cleaner.

HTH.

I find it hard to believe the 07 manual say apply, let dry and remove.
That would be a major mistake.  I have a can of GM Glass Cleaner
#89021822 and it say lightly mist then wipe until dry.

The stuff works okay but I use car wash soap on my C5 glass top.  I have
had the 01 Coupe since Sep 2000 and the top is still perfect.  Just use
what you have and don't worry about it.