How's the tank coming along? Thanks for letting me tag along and learn a bit yesterday.
As for the painting the PVC the guys at SW City told me a year ago that I could paint my spray bar so that it wouldn't be so obvious and I did. They suggested using a Krylon paint so I did. It worked great. I let it dry for a couple of days before installing it and it looked great. I am going to do the same with my new 180 spray bar too. Hope this helps.
I've had couple of return elbows painted black in my tank for over a year and it seems fine. I let mine cure for several weeks before I put them in the tank. You bet you have almost a full can of black spray paint lying around that should work well.