Sarcoidosis is an inflammatory disease. Lymphocytes become over-active which results in granulomas. These granulomas can show up most often in the lungs, but are also known to be found in the liver, lymph nodes, eyes, and on the skin. Pretty much any tissue in the body can be affected.
Based on the actual description of the disease I'd think the very first step would be to focus on ways reducing inflammation. This is as simple as changing his diet. (but not necessarily easy!

) Reducing stress is also important, and of course there are numerous supplements and herbs that are specifically anti inflammatory.
Especially since the treatment prescribed is prednisone, I'd also approach it as an autoimmune disease. The natural path to healing autoimmunity is very similar to healing inflammation....all the same antiinflammatory diet and lifestyle, and supporting antiinflammatory supplements.
I found some hints online that, at least in some cases of lung sarcoidosis, there is a viral component. That would make sense as often there is a pathogen that triggers autoimmunity. In that case, some herbs with antiviral, antibacterial, antiparasitical properties might help.