It is my understanding that the POR-15 leaches into the metal. The surface must be clean of any grease or contaminate. Even wiping the surface down with a chemical that will leave a residue will not give the best results and at worst could cause the paint to peel in a large sheet. I have seen where the POR-15 will fish eye from things like fingerprints or minute amounts of grease.
I cannot say what the results would be with the etch primer. POR-15 does not adhere to other paints, although it will adhere to itself if applied within a few weeks.
The manufacturer also says you need to do one very light coat, then once it has cured, you can go with a heavier coat. Once that coat starts to cure, but you can touch it with your finger without getting paint on your finger, you can top coat. I find that top coating with an enamel at that point the much cheaper enamel will take on some of the properties of the POR-15 like the hardness and resistance to brake fluid. If you wait until the POR-15 has dried, then you have to rough sand it, prime it and then apply your top coat.
If you feel your metal is too shiny, rough it up with some 100 grit emery cloth. That will give the POR-15 something to cling to.
I normally sandblast before applying the POR-15, or else have painted it over rusted surfaces after hitting them with a wire brush to remove any loose material. Both ways look great.
I have sprayed POR-15 form a gun, but you will want to wear a full face mask at a minimum if you go that route. You will also want to clean your gun fairly quickly afterwards. I use xylene to reduce it, and xylene to clean up afterwards. I'll also use it to clean any that I get on my skin. It won't clean it up completely from the skin, but it'll come close. Otherwise, you will be waiting a couple weeks for the top layer of your skin to shed before the paint is gone from your hands. Surgical gloves come in handy when painting or moving freshly painted objects.
There is another thread from not that long ago on the POR-15 and the experience of others. Check it out here:
http://www.mapleleafup.net/forums/sh...ighlight=por15