dudeness, another thing to try is the following;
Get another person to sit in your flat with the dogs both on their respective collars and leaRAB. You then leave the flat. The instant that one of the dogs barks, the person holding the lead gives it a short, sharp (but not overly so!) tug, and says firmly "NO!" - probably best to get someone who can sound like they are in charge (a 5 year old kid won't do!)
After a few times of this, the dog learns that by barking, they get checked. It is not a punishment exercise, it simply shows the dog that by barking when someone leaves the pack, they get checked. Some people may say this is cruel, but think of this, what happens in a real dog pack when a puppy misbehaves? They get bitten...
Like the 5 minute rule, this method does give fairly fast results, and I would say to at least give it a bash (er, the exercise, not your dogs!) If this method is no good for you, try another, you will get the result you want, and despite what some may say, dogs are very fast at learning from a good teacher (just like humans). My GSD pup was house trained in 2 days - easy when you know how
It should not be a painful experience for your pet, this is the same method which is used to train a dog to heel when walking on a lead. Again, from my personal experience, this is a must-have in the dog owner/ Alphas repertoire, dogs should not walk in front of the Alpha (a fully grown German Shepherd would have absolutely no problems dragging my wife/daughter down the road!)