Bill, just as with anything in working on old tin, typically any "short cut" is going to have repercussions or additional steps needed, and is not always the cut and dry next thing since sliced bread that the manufacturer's make them out to be. Any paint stripper will strip again (continue to strip?) so his comment goes without saying. By the same token, not all epoxy primers are compatible with rust convertors, so any residue of that left in pits or otherwise can also cause delamination of the paint if the epoxy doesn't get along with it.. I would agree that the MEDIA blasting (not sand) is a good method to use and gives a good abraded surface for epoxy to adhere, but you best be dam sure the one holding the nozzle knows what they are doing or you will go crazy trying to fix all the warped metal. If your PPG dealer is the only game in town, maybe it's best to use that product and just figure out your best course of action to address any rust issues and also keep the various products playing nicely together. There are ways to use these products together by neutralizing any acid or rust converter, but the person doing said work has got to be thorough to eliminate all possible residue, as the PPG rep stated. As you are starting to see, rarely are the shortcuts actually shortcuts.
Hindsight, what I have in the shop should have been epoxy primered when it was stripped and then cut out any rust issues as they are found/able to be worked on. Keeps flash rust from coming back, requiring more prep. Sure, you may be wasting a bit of paint, but then if something is Swiss cheese from rust holes, don't paint that part.
