Loki has a pretty big bark too - and when we have to stay in hotels with him during shows - we have to control it. We've never used the collar you've mentioned. We did, however, teach him 'Enough' and that gets the barking stopped.
Have you tried other methods besides this collar? In general, I'm not a fan of spraying collars - the spray lingers past the fact when the dog has stopped barking. Also - another dog barking can trigger the spray too