Robert I've followed your work and tutorials on patch panels and learned a lot.thank you.
I was going to use PPG put there prices are crazy high. To high for someone like me that's going to make lots of mistakes. I'm thinking I'll be using a sand able epoxy primer.
Bill
Bill, I've not used PPG's DPLF to have first hand experience, but from what I've read in online comments, it is not a sandable epoxy, which is why the K36 is sprayed over the epoxy after it has flashed; the K36 is sandable. On the plus side, for those who use rust conversion products, the DPLF is apparently compatible, where the H/K and SPI are not. There is a process to clean and neutralize a conversion coating where one could use these primers, but all it takes is a bit of residue in a deep pit to create a delamination/lift in your nice fresh paint job. And of course, both H/K and SPI state their product is not compatible with the rust convertors, so it's a roll of the dice as to whether you get all the residue cleaned.
I just purchased some SPI, which was $177 for a two gallon kit (delivered). H/K runs about 250 for a two gallon kit, or about 320 if you'd like it in quart cans,
plus shipping. I don't know what your PPG is running, but that will give you a comparison. I don't use the conversion coatings, so the H/K and SPI work for my applications. This is my rust converter:
http://i5.photobucket.com/albums/y167/rmccartney/Metalworking/Picture026-2.jpg 
Please don't read any of this as me saying not to use PPG. A person has to look at all the processes you plan on using, and make sure ALL the products are compatible, from start to finish. And a lot has to be said for availability. If your local paint jobber carries PPG and is convenient (open) on the weekend, it weighs a lot on your decision of which product to use. It's nice to have a fall back when you run out of something while spraying on a Saturday morning..