Okay...now we are getting important information...first thing you need to do now is stop. We want the paint to stick...if you say you applied Epoxy, in this arena, that means Primer...there's a big difference between Epoxy resin with black colorant and Epoxy Primer. What grit of paper did you sand it with and why did you buff it? Epoxy resin with black colorant will be shiny when it's buffed, however, your paint will not stick to a slick, buffed surface. If your going to apply the 2K Primer over top of your Epoxy Resin...it can't be shiny...you won't have any mechanical adhesion. You are going to need to sand the Epoxy Resin that you applied with a 400 grit to 600 grit wet paper, it should not be shiny, it should be dull, that way your 2K Primer will stick to the Epoxy Resin. Once you apply the 2K Primer...that in turn, when cured, will need to be sanded so that it looks dull, then apply your paint.
Why did you apply the Epoxy Resin with Black colorant in it? Was this to repair some areas that had cracks in the original substrate? Please answer these questions...I just want this to turn out for you. Using an HVLP Gun isn't going to change any of the characteristics of the material your putting on the Seadoo.