If you look at
these tables, you will see that Silver Chloride is quite soluble in Sodium Chloride, but that Ammonium Chloride works even better. Silver Bromide and Silver Iodide, of course, won't be easy to fix that way, but fortunately most common table salt contains Iodide which works as stabilizer. Likewise, the Thiocyanate you mentioned as anti caking agent will rather work as stabilizer, not as fixer.
If you have to fix film and just can't possibly get your hands on any trace of Thiosulfate, I would recommend multiple bathes of concentrated Ammonium Chloride at elevated temperature, with each fixing step no longer than 10 minutes. There is no need to wash between fixing steps in such a setup.