My cat, Kat, has suffered terribly with urine scald for months. I tried everything except human baby ointments because they contain zinc which is poisonous to cats, not sure about dogs.
I can't get Bag Balm here in Spain, but I learned about Cavilon, made by 3M, from Bendy's mom, who is an expert on urine scald, she used Cavilon on Legume. It's a clear spray that you put over the damaged skin, it protects the wound from the urine but lets it "breathe" so that it can heal. A bit expensive but well worth the money, it is used on humans for ulcers, pressure sores, etc. You should be able to get it from any pharmacy, or they can order it.
Kat's urine scald was terrible, the Cavilon improved it slightly, but it had got to the stage where she was bleeding and had necrosis of the skin. The vet, desperate by then, put her on antibiotics normally used for leprosy, that he uses for dogs with bad skin problems (I think it's called Rifampicin in English). I tried everything, and the best (only?) thing that worked for her was honey. It's pretty gooey to apply, but it protects and cures, I researched it on the Internet. Her "rear end" is now back to normal, and I am maintaining with just the Cavilon (I sometimes use an iodine spray underneath as an antiseptic if she is bleeding). With the honey I saw an improvement in a couple of days, it took about 1 month to heal up completely, but it has been the first time since I adopted her. Once the skin's better, Cavilon works great.
I recommended honey to someone else whose cat had the same problem but they didn't have much luck (they are using Calendula cream, which I also tried). Honey isn't easy to use- I would put it onto Kat's rear and as it was impossible to put a bandage there, some would inevitably drip onto the floor, it made a mess, but in the end it was well worth it (I have to clean up after her constantly anyway!)
Sorry, message longer than I intended! Please let me know if you find anything else that works...