I've done zero prep and by far the best shine I've seen is this......
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I don't prep because with Jeeps that go off-road, it would be futile. This stuff always amazes me, even after washing days of sand and mud off the Jeep. I've used it on white, bright red, and dark blue. It pops on all 3, but especially the red and white.
The best part is that it is only about $26 on Amazon and one jar lasts a long time. I've done 4 vehicles and hardly used any. It lasts a long time, too. I put the first coat on a Jeep in March and it still looked great and beaded exceptionally well when I did it a second time last week.