I don't know how uniform people can paint their screens on wood or dryboard or whatever, but I just thought this might interest some people.
I've been using bedsheets from Walmart(TM) http://www.avsforum.com/ubb/smile.gif
as my screen. I used larger black bedsheet on the back, and then put two layers of white bedsheets in front of that to make my screen. Blacks that surround the white makes it look nicer, BTW.
Anyway, I noticed that because the fabric isn't dense enough, it leaks light. I put aluminum foil behind the white bedsheets and it shows higher brightness. Unfortunately, it made the screen even less uniform.
So, I said, heck with this! I painted the bedsheet with ultra-white flat paint. FANTASTIC! Thanks to the fact that fabric absorbs the paint, it turned out extremely uniform. As I type this (and viewing it on the screen), I can see excellent contrast and uniformity.
So, basically, if you cover whatever screen material you're using with a white fabric and then paint that, you might get a better uniformity out of it.
There might be drawbacks, but I don't know. This looks fantastic to me. It kind of automatically gets perforated too (depending on the fabric and the paint).
Just thought maybe people might be interested.