If it is warm enough, you may want to consider giving him a bath with a medicated shampoo, like Eqyss Micro-Tek Shampoo. I would also consider clipping him. Even if it is a bit too cool to clip him, you could blanket him to keep him warm. I would also condition him really well after the bath. I would treat him daily with some sort of medicated spray to help him with the itching. If it does not clear up within a week or so, you may need to call the vet out to test the skin. He may require prescription grade medications to help him keep comfortable.
I hope he gets some relief soon.