Hey, I got a English Mastiff and every summer he gets hot spots on his tail and hind quarters. I did every thing under the sun to clear up the problem. I never went to the vet because I'm always strapped for cash. Even though I consider him part of the family (a very important part) the rest of my family always comes first. So I feel your pain when it comes to fact you don't have the money to take him to the vet.
Anyway, I was shopping at Walmart and found this stuff and it worked miracles for him. I started to spray him with it 3 times a day and it got to the point where he was ready and willing for me to spray him with it and he began to like it. When I broke the bottle out he would come right up to me ready to get his ass sprayed with it. He was cured in less than a week.
Here is the link.
http://www.walmart.com/ip/Pro-Pet-Hydrocortisone-Spray-Itch-Relief-4-fl-oz/10318456
Now I'm not saying this will work for you but it's cheap and it's all I use when he has skin irritations like you have described.
Hope this helps you out and I hope your dog gets well soon.
Peace.