I've not used the Omni primer. I have shot the Omni paint and it didn't seem to cover as well as the full-blown PPG paint.
I use the NCP271 (?) high fill primer with the catalyst from PPG. It sprays thick and fills pretty good. Almost reminds me of the old Featherfill from way back.
I would suggest getting the tech sheet on this. With the DPLF primers, you can only spray the NCP over DPLF with the 402 catalyst (it may be 401, I'm going off of my memory). The tech sheets for the DPLF and the NCP clearly state which DPLF catalyst you should use.
My local PPG supplier told me that the Omni paint is about 1/2 the price compared to the PPG paint. Great for bodyshops with pro's behind the gun, but I thought that is was real "watery" and didn't cover as well. Could have been just me.
Also catalyzed spot filler called "Icing" works real well on pits. I just finished a M/S 80 gas pump that was pitted really, really bad.
Hope this helps.