My vet's office used to get alot of Golden Retrievers in with hot spot, like Keegan. I've heard that it can be started or worsened by diet but also with moisture that stays on the skin. Alot of Goldens swim and the dampness can stay in their fur and irritate the skin that they then scratch and it progresses from there.
I think you're right, it probably is from the scooting. And, maybe there was some moisture there from his messy bum and it just got worse. Hopefully the vet will check his anal glands to make sure they are not impacted as well.

I haven't tried this but I've been thinking about it. My vet suggested that I take a box and cut a hole in it on the side that is big enough for my smaller cats to get in and out of easily and put a bowl of food in there for free feeding. That way, my two big guys, George and Paddy couldn't get in to eat because they are too big to fit through the hole. They would only get food when I give it to them twice a day. Sounds mean but it might be a good solution.
Right now, I put a large bowl of kibbles up on the window sill. Everyone who shares Paddy's room can hop up there but he isn't able to so it's pretty much the same thing I guess.

I was just suggesting to Moesha that she might want to ask her vet if the antibiotic Convenia injection would be applicable in Aroara's situation. Maybe it would be for Calloway too. I think I remember reading that it was good for skin and bacterial infections. Here is the website link: Convenia
It would be great if you didn't have to pill him twice a day.