I don't think it is required unless you feel the paint needs a bit more cleaning. The first layer of AJ will just be a bit harder to apply, as the surface will not be as slick as after Prime.
What evidence is there to suggest that Prime offers a superior base over bare paint, if the surface doesn't need any more cleaning/polishing?
mburnickas,
Why do you need a good basecoat? Do you get better depth, durability, or shine?
Not being argumentative, but trying to understand the logic behind why it is required as you say.
- Justin