I did many searches before building my screen. Here is the best that I found. Extremely strong frame that won't twist or warp. And lightweight to boot.
DIY Frame
I bought my 1x3 pine from Home Depot. Dig though the pile and make sure you only select straight pieces.
In the above plans, he used a 1x8 header plank, which is a nice touch but not neccessary. 1x3 is plenty strong enough. He also uses velcro to attach his screen material. Whether or not you decide to do that is up to you.
Any fabric store will have blackout cloth, just make sure that it is 100% blackout.
I didn't paint mine and have no intention of doing so. PQ is fantastic. Although the cloth is inexpensive so if you wish to experiment it won't break the bank.
Total cost for me was $60 CDN for the whole thing.
Here's a link on how to stretch canvas. Use the same technique when stretching your blackout cloth.
Canvas stretching