I actually did send you information on OSPHO and on SPI Epoxy Primer in a Private Message about 30 minutes after my last post to you. If you didn't get it, I will resend the information. Lizer did explain the difference between Epoxy and 2K Primer. Never apply 2K primer over bare metal, it doesn't have the corrosion resistant qualities that an Epoxy primer does. A good 2K primer is great for achieving build but, somewhat like lacquer primer, it's porous and allows moisture to penetrate through the metal and rust to form underneath. A good route to take is to apply two coats of Epoxy Primer, allow proper flash times and the 2K primer over top...now you have the rust resistance of Epoxy and the build of 2K primer.
2K primers can shrink...if they aren't used properly but, when used properly, with the right amount of time between coats they are an excellent product.
I will resend the information, let me know if you get it, if not we will figure out another way to help you.