Which treatment works the best and fastest for vasculitis?

Depends. Vasculitis is a generic term for vascular wall inflammation. The causes of it are multiple and each cause has its own best/fastest treatment. If you know the cause, let us know it too. That way we can suggest what's best in that case.
Type and severity. Treatment depends on the type of vasulitis which are many, the severity and response which varies. Steroids are the mainstay for many different types. Drugs such as methotrexate, azathioprine, Cyclosporine and Cyclophosphamide are some of the agents used. Surgery and stents may be needed in select patients to restore blood flow to vital organs. Vascular and rheumatologist consult recommended.