What is the best way to deal with a patient with interstitial lung disease?

Depends on the cause: Interstitial lung disease is not one problem, it's many problems with numerous causes. When you know the cause the best thing to do is treat the underlying cause, but when the cause is unknown it's referred to as "idiopathic". Idiopathic interstitial lung diseases are often incurable, and in particular idiopathic pulmonary fibrosis has no treatment. Many are referred for lung transplantation.