This thread does not promote a solution of my own creation. It is more of a digest of information that was first presented by bud16415 in his thread A Simple Screen Paint Solution. It also relies heavily on the work and presentations of wbassett regarding off-the-shelf neutral gray paint tints. I'm not sure who first introduced the idea of adding waterborne polyurethane to paint but pb_maxxx has long been an advocate of the Minwax Clear Satin Polycrylic as a paint mix component. In the Beginner's Guide To Simple DIY Painted Screens I tried to summarize a lot of what I have learned from this forum and my own experimentation, but there is a lot of information and some may find that thread a long read.
This thread is intended to offer a simple and effective alternative to the big three DIY Screen Paint "Mixes". It is not meant to discourage anyone from trying Black Widow, Silver Fire, or S-I-L-V-E-R, however I would suggest "Beginner's Delight" is a good place to start. You will have an excellent screen surface that will work very well with the current crop of bright high contrast projectors and provide you with a solid basis for comparison if and when you decide to make up a sample panel of any of the aforementioned DIY Screen Paint Mixes.
What to Paint
Any surface that is smooth, flat, and that paint will adhere to. The simplest thing to use is the wall. Fix any bumps or dents and wet sand if the wall already has roller texture. The smoother the better. Recommended reading.
To Prime, Or Not To Prime
For truest color, it is always recommended that apply one or two coats of good white primer. Painting a screen is no exception. If the wall is already a uniform white and you are using a self priming paint, then maybe you can get away without priming. A white primed wall also offers an opportunity for you to see how well a flat white screen surface will work in your room with your projector.
Primer IS NOT Flat White Paint
Primer is formulated to provide a white surface that is porous to promote paint adhesion. This fundamental characteristic makes it a poor screen surface because it is neither durable or washable. If white is right for your situation, then use a good white base paint.
The "Beginner's Delight" solution will be presented in two flavors. The first flavor is "BD OTS Matte". While it is true that we now know how to tint most paint bases to some shade of neutral gray, you should not just use any paint base. The second flavor, "BD OTS+Satin", is technically a mix, but a very simple one. It is simply any one of a number of OTS neutral gray paints mixed with Minwax Clear Satin Polycrylic.
Getting Paint On The Wall
With the "Beginner's Delight" solutions you can achieve excellent results by using a roller and a simple application technique. I am in no way apposed to spraying these solutions but I have no experience with spray painting and will offer no suggestions or comments regarding spray painting. For those curious about or interested in spray painting, I do recommend you take a look at this post in the Beginner's Guide.