I still have my Aurora Model Motoring HO scale slot car set from when I was a kid (early 1960s)...my HO train set as well. They're stored away...not sure what I'm ever going to do with it all...hopefully my daughter might one day have a boy I can pass it on to. I've checked eBay...this stuff...
Griot's Premium Carnauba Wax is outstanding. I think it's a Pinnacle Souveran killer considering it's less than half the cost of Souveran. It goes on very easy and buffing off very easy as well. As far as durability I can't say...the car is garaged and doesn't see rain so longevity isn't an...
I have the 3M clear bra on one of my Avantis and had it done about 2005 or so. It's never given a problem but admittedly the car stays garaged.
The only negative I've experienced is sometimes someone will ask about the "scratch" across the hood when all it is the the edge of the clear bra...
I can't say for sure, but since automatic car washes apply liquid waxes I see no reason why your applying a sealant would be harmful. Cars and trucks go through all kinds of slop and weather so a glass sealant should be a help.