Formulary Potassium Ferricyanide (Bleach) Powder 1 Lb. (this is a rehalogenating, right?)

Unless it contains Potassium or Sodium Bromide, or Chlorise on ut's own Ferricyanide is not a rehalogenating bleach.

Some people use a plain Ferricyanide bleach (no bromide) others add bromide, and if you add Thiosulphate to plain thiosulphate you have Farmers reducer.

There's no set rules, papers vary substantially as Bill says soit's trials and experiments first to get the effects you desire.