I go through a good bit of Kosher salt, making duck prosciutto, making Gravlax, making brine, curing meats for confit, baking fish whole in a salt crust. I have always used Kosher salt, mostly Diamond Crystal (DC) at $2-3 per 3lb box.
It occurs to me that restaurants and other food preparation services making the same sort of charcuterie aren't using Kosher salt. Brian Polcyn can't be buying his salt in 3lb boxes. I contacted DC and inquired as to if Kosher salt was sold in 25-50 lb bags for commercial use and was told it was not.
Today I was passing by a restaurant supply hat sells to the public and I purchased a 25lb bag of DC "Granulated Salt" for $5. It's pure salt, no additives, no iodine, smaller granules than Kosher, not flakes, but much larger than table salt.
I can see no problem substituting in brines, stocks, etc. but what about curing meats and fish, will the shape make that much of a difference?