They come out at 3 different pH's, so are wonderfully useful in lots of different plating solutions. It has a tendancy to make the plate white or bright, this is because it maintains the pH very well. Higher ph's tend to give a dark or even black look that is sometimes rough. A buffer is a chemical that will resist the change of a pH in either direction. Flourine is a gas that is extremely active and very dangerous.
Fluoboric acid is much more common in plating baths.
Ammonium bi flouride is the safest way to get the flouride ion as hydroflouric acid is very dangerous, possibly the nastiest acid to work with in a concentrated state. I can not imagine a use for barium sulfide as barium forms rather insoluble compounds as does sulfides. Barium sulfide should be extremely insoluable. Both are hazardous materials and require special handling, more so than than some othe plating materials. We sell a lot of barium sulfide here at Bryant for use in putting blue and brown coatings, or patinas, on metals like brass, bronze, and copper.