A really good spray wax / quick detailer which provides much greater protection and water beading/sheeting ability than standard QDs and that you might want to check out is Britemax's #6 Spray & Shine, as it's got real carnauba wax in it. It's fine on the finishes typically under a show car and much faster than doing it the traditional way with a 'regular wax'.

I also own a concours car, painted underneath and I've owned and run detailing forums for 10 years so although I wouldn't claim to know everything, I do know a bit