I would highly recommend calling your farrier and vet ASAP. You don't want the problem to escalate. He's at greater risk of developing an abscess or something worse if his feet are that bad.
In the meantime, I second the epsom salt/warm water soak (maybe 10-15 min).
If he has visible thrush cracks in his frog like my horse used to get, I recommend getting some gauze pads, dipping one in something like kopertox or really any thrush meds, and shoving it into the crack with your hoof pick. He won't like it, but it'll keep dirt out and the meds in.
Once, when my horse had some REALLY bad thrush, I used one of these
. I put about a third of an inch of epsom salt covering the inside bottom of the boot, added maybe a tbs of iodine, and stuck his foot in there. If I recall correctly, I changed it 2x a day and used it for a week or two.
Also, make sure you are controlling the environment around his feet. If he's stalled, clean it 2x a day and keep lots of clean dry shavings in there. If he gets turned out, try to avoid soggy fields, or limit his turnout if it's wet everywhere.
I hope some of that helped!