I used regular por 15 then either black coat or royal blue flex coat to top coat.
It was the flex coat that caused a problem. The primer we used, House of Kolor KDA3000, had a bad reaction with it. Within a few minutes of the primer being sprayed a few sections just peeled off and it was as if the flex coat never cured. Kept having to wipe up what I could and spray more primer.
The flex coat had a month to cure and was sanded before we primed, it was probably just an issue of compatibility of the products.