Projection Surfaces
You can project on almost anything to varying degrees of success. Water? Not so good. Mist? Can be good.
The one thing you can't really project is on to a surface that is getting direct sunlight during the day.
Projector Paint
I've used all kinds of things. The thing that looks best is Screen Goo IMHO.
The version of Screen Goo I like best is: Screen Goo 2.0,Max contrast (.7 gain)
Have A/B’d against Paint on Screen Projector Screen Paint G005(S1 Screen Plus Silver) (1.4 gain). The difference is marginal, but enough to notice that the Goo looks better. How these compare to just a basic matte grey: also marginal.,
You can blend on the Goo and not worry about brightness changing based on the viewer’s relationship to the screen. If you walked through Penn Station between 2017 and 2020 you would have seen a 2 projector blend using a screen that’s treated with reflective properties in order to increase the projector’s gain, that when standing in the middle of the room, looked good, but when you were offset from the middle, one side of the projection would appear way brighter than the other – making the final projection look like complete shit. It's a miracle it was a live presentation for that long given that I would call it “very bad.” (FYi, a few of us worked with the company who developed this screen material, they’ve since gone out of business, and I think now are getting into edible products… rich people am I right? yikes!).
What else works is : gray paint. A gray that is 75-85% white (or 15-25% black) looks fine 95% of the time. Budget for Screen Goo, then when things get tight, hit up Benjamin Moore. Just make sure you do an eggshell finish! None of that glossy nonsense.