You will need to get rid of the fleas before you will be able to get the hot spots under control. Treating the house and environment to kill the majority of the fleas is helpful. There are also topical flea products available from stores but that means the flea has to bite your dog in order to be killed.
Using Defendex Shampoo can provide topical relief to your dog. In addition I find using our homeopathic product Derma-IonX can be helpful in helping the body reduce inflammation allowing the hot spots to heal. Omega 3,6,9 can also help to reduce the inflammation and improve the skin.