Dorwest Tree Barks Powder

Dogs eat grass usually either behaviourally (as a habit) or because they feel nausious. Tree Bark is a herbal supplement that anecdotally helps settle the guts, this means it might have this effect but it has not been proven to do so.
Preventing the nausia or training your dog not to eat grass is the best approach. I advise following your vets advice closely on how to do this, especially if they have already advised a veterinary diet like Hills ID.

This supplement will not change the nutritional requirements for your dog, I would advise adding it to the normal amount of feed to you are currently giving.

It sounds like your cat will need an different approach. I am not sure that the Tree Barks powder will be effective even at a higher dose given what you have said. Ideally he should see a vet who could check him over and make sure that there were no other obvious causes for this persistent diarrhoea. If nothing is found, then I would suggest changing the diet to something significantly different to what he is on now. There might not be anything "wrong" as such with the diet, but it is possible that he has developed a sensitivity or allergy to it, or in some other way it does not suit him. He should go on to a simple, good quality cat food based perhaps on either chicken or fish, but different from what he has been on. You could give him a probiotic too for a while and see how things went. If he has not had a worm dose for a while that should be done too. Failing all that, your vet could do some tests which might reveal an underlying cause, so that could be worth following up. I do think that 2 weeks is long enough to decide to try a completely different approach than the Tree Barks product, even though that can be of benefit.

This sounds like a slightly confused situation. Anal glands not emptying properly is common in some breeds, though can be helped sometimes by adding fibre to the diet, such as Protexin Pro-fibre. Anal gland trouble will not normally cause leakage from the anus, though anal gland contents themselves might well leak out (quite unpleasantly). The Tree Bark Powder is felt to help with many dietary problems but is very hit-and-miss. It does seem to help in many circumstances but there is not a clear scientific explanation of the mechanisms involved and undoubtedly it will not always help at all. It seems to be safe to try.

Tree Barks Powder would be a good supplement to give your dog while you are trying to identify the problem. It is possible that with some help from supplements, your dog will get over the current condition. However it is also possible that there is still an underlying problem which would be best treated by a specific, well directed treatment. This can only happen with a proper diagnosis. Negative results so far just means of course that the cause has not been identified, it does not mean that there is nothing behind the symptoms you see. Referral to a specialist might be needed. Ideally you should try supplements but continue further investigation if symptoms persist. I would also try adding fresh ginger to his diet (the sort of amounts used to flavour oriental food) as well. This can reduce feelings of nausea in some cases, which it sounds like your dog is experiencing.