Ulcers are typically a secondary infection to something bigger that has happened like an injury, a virus, parasites, water quality that is off, etc. Here's some options that are dependent on how aggressive you want to be:
1) If it's really bad he can get a vet to help him out with some Baytril and inject it. In bad cases injectibles is really the only way to solve the problem. You inject every day for 3 days and then every other day for 2 more days. Amount depends on size of the fish.
2) Tricide-neo. Great stuff for body ulcers. Really great if you're not a fan of injecting a fish. You can get it here:
https://www.pondrx.c...ucts/16166.html. You basically mix it up with distilled water and pop it in a spray bottle and spray the fish. It's long lasting stuff and can sit in your refrigerator for over a year.
3) Option 3 is to quarantine and use
Nitrofuracin Green that you can buy
here (scroll down the list) and other places. Prob is, you've just hit the holidays and you've gotta get the stuff in hand--so not sure that fish can wait until you get this stuff in hand. I prefer Tricide-neo, but there are folks that love this stuff.
4) a PP
(potassium permangante) poultice. Get this stuff and make a poultice and rub it into ulcers. You can usually find this at better koi/pond shops...not at places like Petsmart. Stuff is powerful and not to be used lightly. Can kill a fish if not used properly, but does wonders when it is.
5)If you've got nothing left or don't want to do the stuff above, clean with peroxide and use iodine for a few days. This is the most benign thing to do and will likely have the smallest results from all those listed above. You can also couple this by using malachite green and/or formalin which is available in lots of products on the shelf...QuICK Cure is one of them and can be found in any fish shop. Say prayers.
I hope others can offer you suggestions as well. Salt may aggravate the wound, so I wouldn't use that. Get that Ph down too. But you've gotta figure out what has caused the ulcers to begin with...otherwise they may just persist.