This is a great product, used in conjunction with the spray collar, & does indeed give fast results to stop a barking dog.
However, my little dog shows her super intelligence (or maybe stupidity!) by continuing to bark annoyingly once the collar has been removed.
In other words, it is not training her against barking but just stopping her at the time.
We have had similar results with other behavioural products so the fault seems to be with our mutt rather than the actual product.