My guy has chronic lymphangitis, so a bit different than cellulitis, but essentially same treatment. I think it really depends on the horse what works best, so for my guy, I do the following.
As soon as a flare starts he gets a full dose of banamine and I get him moving. He is usually on 3 legs when I first find him, but after 15 mins of walking he is just “off”. For him, movement helps a lot! As soon as he can tolerate it I do a tight compression wrap with a pillow wrap and standing bandage. I wrap from heel bulb to the bottom of his hock. No cold hosing, his leg doesn’t swell with “hot” swelling that would make cold hosing beneficial. He gets put on a high dosage of bute (4 grams in the first 24 hours, 3 grams in the next 24 hours, then 2 a day for at least a week) and we hit him hard with antibiotics. We’ve used…gent/SMZ’s, gent/excede, and baytril, on different occasions of course.
He is turned out as usual during the flare, and re-wrapped several times a day.
He is now at the point where he needs to be wrapped 24/7. Annoying, but worth it for the health of the horse. Flare ups are scary because each time, the leg could go septic and I would have to put him down. Cellulitis/lymphangitis is not something to be treated lightly and I certainly would not be treating with only SMZ’s unless it is the first flare and very mild.