Making a better salt fixer

As I already told you in this blog (see recipes) sea salt may be used as fixer if you use a very concentrated solution, for me it works with 300g per liter solution, and the warmer the better. At 40ºC you may fix a B&W film in one and half hour. Many people will find this time still too long, although they are developing with rodinal in 2 and more hours. But if they may fix in 5 minutes with ammonium thiosulfate, why then salt in 2, 3 or more hours according to temperature and concentration. For this reason I am now looking for an additive to salt, easy to get, that would make this fixer faster. I already tested two of them, sodium fluoride and potassium bromide. Both act as accelerators but potassium bromide, for the same weight, is faster.
I have been using 0,2 g Kbr per liter, adding more brought no advantage. Very small amount for a large time reducing, almost 40% less time needed to clear and fix.

The same salt solution with two different additives