Your gonna wanna get the por-15 tiecoat. Because if you want to paint over the por-15, not gonna happen, so spray the por-15, then when the por-15 is still tacky spray on the tiecoat and after that you can do what ever, undercoat, paint, etc. And just a reminder, DON'T use por-15 on clean metal. It does not bond well and is a pain if you sand through it.
Hope that helps,
John