I'm sure I have but don't remember for sure as I have been doing this for many many years.
When I use salt (which is rarely), I grind up Kosher salt because of less impurities and it stays suspended better when it is powdered. Additionally, when you use salt it will take more colorant.
Here is the ratio that I use: 1/2 cup plastic, 1/4 cup salt, 3 tbl sp softner.
Remember salt is there because of it sinking quality so stir, stir, stir, stir.