Etch primer is good for smooth new metal. It etches the metal so that paint will stick to it. You can't use filler on top of it.
When to use etch example: Let's say you have an exterior door handle that needs to be painted the same color as the car. It's hard to sand all the little nooks in and around the handle. Spray it with etch primer and it will help eliminate any areas that you could not sand very well. You will still need to seal the etch primer. And that is done with the epoxy primer as a sealer.
Epoxy is hard, non filling, non-porous and sticks like crazy. You can paint anything on top of it. Eurathane, polyester, enamel and POR-15.
Here is a little hint:
Let's say you've had the whole car/truck sand blasted. You have a lot of shiny metal that is going to flash rust in a hurry. A single coat of Epoxy will prevent the rust from forming.
So now you have a fender or two in one corner of the shop, a hood over there, rear fenders stacked in another corner, doors standing against the wall. And you can't do all the body work that needs to be done within the next week and if you wait longer, you will have to scuff all that epoxy.
So what do you do? Well, when you got back from the sandblaster, you applied a coat of epoxy. If you apply two coats of 2k as soon as the epoxy flashed you will have covered all the epoxy. Now all those parts sitting around can wait until you get to them to do the body work. The 2K is a lot easier to sand than the epoxy, and plastic filler will stick to it.
The best filler I have found is Z-Grip by Evercoat. It will stick to anything, so don't drop any on anything you don't want to sand. Why pay the extra price for Rage filler when Z-Grip is just as good. It makes for a smooth application without a lot of pin holes, sands easily and doesn't clog your paper, thus saving money on sand paper.
I own a body shop, and I don't have any etch primer in my shop. There is really NO need for it.
If you want to see what we do at my shop, check out the two links in my signature.
What we are doing in my shop 2010 Challenger with painted lazor stripes and logos Frank Cox
Cox Custom Cars
