omni over concept

I was wondering if I can spray omni MTK over Concept without priming it. I sprayed concept on some parts the last week and did not like the shade of yellow. The more I looked at it in the sun the more I hated it. After trying a few differant colors I finally got what I was looking for. So now I want to cover what I already did in the other shade with the omni.I am not talking about any body parts , they are just rear end parts that I have painted already. Also I have some PPG epoxy primer , will that work with the OMNI MTK or should I play it safe and get some OMNI primer.
Thanks
Angelo

The primer doesn't matter you can use EPX 900 or whatever under it and will be fine. You can spray Concept over omni or omni over concept. Just make sure to wet sand the piece back down correctly or scruff it to hold paint again. IMO, PPG needs to be sanded down with at least 600 grit to not show sand scratches. The paint rep here said he does it with 320 or 400 wet but I can't see nor believe that since I still see the sand scratches from it. don't forget, there is also Omni Plus now too.