Church, Bistro and Theatre

The sanctuary is fairly large, and has a moderate echo already. I am worried that the new paint will deaden the reverb, and am trying to find a paint that will keep the surface as hard as possible (even if it means repainting a coat on top of the pigment coat.)

The church uses traditional music, choir and organ, and so would favor a live acoustic.

Does this paint exist? I’ve heard about it being used, but I don’t know if it’s just rumors. Where can I find it?

I have a fabulous deck I need to spruce up and decided to paint a wooden bistro set, to withstand weather, what’s the best thing to seal it with and still make my paint designs vibrant and lively?