Shampooing will sometimes help to control itching. Some shampoos such as Pyoben and Oxydex, act to reduce the bacteria level on the skin, one cause of itching. Lytar, Clear Tar and other tar containing shampoos reduce itching and oiliness. An emollient or moisturizer used after shampooing will restore some moisture to the skin and this also reduces itching. Expar Creme Rinse can be used to kill fleas after itching and moisturize the skin.
Antihistamines are useful in the treatment of itching in some dogs.
2mg per lb. It might be necessary to get a dosage for your particular dog from your vet for the others listed, because I don't have that info handy. Some pets will become drowsy when taking antihistamines. If this is unacceptable, they can not be used, or might be best to use at bedtime. Fatty acid derivatives compete with aracadonic acid, the trigger for itching in the body.