PPG's DP epoxy has not been available since the mid to late 90's. Its replacement DPLF is another animal and no were in the same league as the old non-available DP.
If one was to go down the PPG route I would suggest the EPX900 epoxy found in the industrial line. Myself and others have found it to be a good product much better then DPLF.
Personally, I now use only SPI, to which I find it as good if not better then the old non-available DP epoxy.
Diamont or R-M and Valspar both make good quality epoxy primers, I have used both.
