The biggest problem with getting advice on a forum setting is that regardless of whether someone knows anything about the paint products you are using, you'll get plenty of advise for rust conversion products without considering those paint products and cross-product compatibility. From SPI's Epoxy primer data sheet:
Precautions:
NEVER use SPI Epoxy over a Soda Blasted vehicle unless you
call us first for proper neutralizing instructions.
NEVER use SPI Epoxy over Acid Etch/Wash Primers or Rust
Converters.
Acid treatments should not be used unless you know the
proper way to neutralize them, again call us first to be safe but
we strongly recommend against them.
If not handled properly the aforementioned issues can destroy
a paint job and will result in an expensive mistake.
House of Kolor also advises against any rust conversion coating or etch primer with their epoxy. No matter what it takes to neutralize one of these conversion products, if some of it remains in the bottom of some deep rust pits (an area harder to get clean), it is sitting there waiting to wreak havoc. With either of the above mentioned primers, and possibly others, all it will take is to sit in the sunlight on a warm afternoon at a car show, and once the acid deposits left on the panel start reacting, you'll have some nice 1/8 diameter circles under your paint where you are experiencing lifting issues from the acid reacting with your primer. What did the paint job cost the first time? Guess how much gets sanded off to fix this mess?
I prefer to sand blast where possible (jambs, inner doors, and any other "creased" areas) and DA or otherwise abrade any flat areas that are subject to distortion from sandblasting. If I run across any pitting, I check it with an ice pick. If it will hold the ice pick, sandblast the pit clean. If the ice pick goes through, the pitted area would have made it through your new paint in the form of bubbling or other defects within a year or two anyhow. I typically cut any pitting areas out and install new metal. I find bright, shiny, properly abraded metal needs no rust conversion, and this abraded metal is a perfect surface for adhesion of any epoxy primer without any fear of lifting/reaction issues.
