John Aalberg wrote an article for FIS. It well written and I don't think I can add to it. See it here.
Salting should be used to save the competition (i.e. make it fair and safe), not just to speed up the snow or make skiing easier.
Use in warm conditions - 0C, 32F and above.
Works best for snow with significant water content. If you can make a snowball, salting may work for you.
Test a small area before committing to covering your whole course.
Allow time for the salt to work before skiing on it. Typically this is 45 minutes to an hour depending on a lot of other factors.
This event was the World Cup at Soldier Hollow, February 2019. The temperatures were right on the edge of freezing. It was a challenge to keep the course in shape.