Do not use real salt! Salt will absorb any condensate in the air and make a mess over time.
I have been to Bonneville and stood on the salt flat. It's very hard, I couldn't kick into it with my heel. It's also not slippery. It had a gritty surface like those non-slip stair treads in an industrial setting, or like walking on stucco. Every so often there would be a small hole in the surface, like a mole hole filled with water. There would also be puddles on the surface in some areas. That's because salt attracts moisture!
Fine sandpaper painted off white (more antique white) would be decently realistic.
Me on the salt. A surreal environment. Interesting that it was so vast and you couldn't judge distance since there was nothing to get coordination from. Those mountains never changed no matter how far we went out on the salt. They could have been 1/2 a mile away or 50 miles away.
The surface up close. Note the small hole filled with water as described above. Surface was like stucco.
Edited by Tom Geiger, 07 October 2013 - 12:28 PM.