I submitted seven prints to the Delaware State Fair one year and simply mounted them on matte and they were put on the wall of a non controlled building. Hot and humid. They made through OK for ten days. A controlled environment should fair them much better. No glass, there's not much you can do. But as long as they don't hose the dust from them ever morning with a garden hose they should come through unscathed.
The wedding and portrait photographers around here have their (c41 color) prints laminated on masonite or mat boards. They usually have a luster finish which looks good for portraits. Don't know how the "art world" would react to that.
What are you protecting them from? No spray will protect the print from physical damage, as glass or plexi would (within limits, of course) but would seal the surface of the image form pollutants in the air and from very casual contact, such as fingerprints. For my money, Renaissance wax is a better bet, since it gives a wonderful sheen to the image, doesn't show fingerprints and wipes clean. More of a pain to apply, but...
For my money, Renaissance wax is a better bet, since it gives a wonderful sheen to the image, doesn't show fingerprints and wipes clean. More of a pain to apply, but...