Supaguard is like a very tough polish/glaze, used to use it all the time at Merc and Porsche dealerships I worked at, it helps stop bird poo and tree sap clinging to the paint work and therefore damaging it, it was also very effective at reducing fading on solid colour vehicles. If you're going to use it on older paint work I'd recommend a full valet including clay, then use supaguard, should be good for three years as long as you use the aftercare pack. If you're applying to an older, solid coloured car I'd also recommend getting the car "mopped" to bring the colour up to spec, keep Supagourd off plastic, it stains like a mofo, wonder wheels from the same company is great at reducing the cling of brake dust and I would deffo recommend the interior protection kit, melted choco bar on the seat.? just wipes off, lovely.
Oh and finally, don't wash the car for two weeks after, it's still curing up to then and don't use Megs deep clean body shampoo, been known to "pull" off the Supaguard. Any questions?