BeEmveh2002 wrote:

I like to use PPG DP90. It's a great etching primer and is just what you need to shoot over different materials like bare metal, filler, fiberglass. After you shoot it, you should go over it with your thick high fill epoxy. Hope this helps, -Cyrus '69 2002 '72 Chevelle '64 Impala Wagon

DP90 is not an etching primer, it's an epoxy primer.
For the PPG Deltron (urethane) paint systems, a self-etching primer would be something like DPX170 (but you can't put DP/DPLF primers over it.)

A high-build primer is not usually epoxy, so if you need one you'd get something like K38. Epoxy does not sand well, that's why high-build primer/surfacers are usually acrylic or something similar.

The self-etch primer is used if you want to improve the adhesion to the bare metal without using a metal treatment beforehand.
DPLF90 epoxy will stick very well by itself, esp. if you use the correct DX series metal treatments (DX579. DX520) to provide an acid etch before the first primer is applied.

The best primer would be the epoxy (DP/DPLF), after using the DX metal treatments. Then a primer surfacer or high-build primer only if you need to level some defects.

All the product sheets are available online here:
http://www.ppg.com/cr-refinish/phase1/frmProductInfo.asp?Cat=9