Thanks everyone for all the great suggestions!!
So Calvin had his vet appointment and it went well. They did shave a big spot and the infection was a lot bigger than I thought. Anyway they gave him a shot of antibiotics that lasts for 14 days and then they gave me a cream to put on 3 times a day.
So this morning I took a look at his hot spot and his hair is all stuck in it again. I am hoping that he will let me use a warm cloth later to loosen the hair and put more cream on.
So again thanks so much for all your suggestions and letting me share with you yesterday I was so nervous. Today is a better day.