What is the best treatment for shoulder bursitis?

I have suffered from shoulder bursitis for the past couple of years. I am convinced it has been caused from years of tennis. It flares up at times and is debilitating, but most of the time it is manageable. I have tried everything short of surgery. The cortisone shots work well, but I am reluctant to have more than two. Recently I have been using these patches from www.osmopatch.com 
they certainly draw out lots of fluid and relieve the swelling. I have found them ver effective when I follow up with some good rest. Definitely give them a go. They aren't very expensive. Not sure if you can buy them in store, but there is a website

I am an extremity chiropractor, and used to treat a national waterpolo team, who develpoed many shoulder problems. 
The most important thing to actually do is have the shoulder assessed by a trained specialist of the shoulder to determine the correct and actual diagnosis. Bursitis can often be picked up on MRI and ultrasound examinations. 

There are many other causes of “pseudo-bursitis”, which often mimic the pain of bursitis. 
The main culprit is the arch above the shoulder joint (called the coraco-acromial arch) often impinges on the bursa and a muscle tendon called the supraspinatus tendon, causing extreme pain and loss of shoulder function. 

My advice, consult a highly recommended practiitoner in your area with specific experiance in shoudlers. It sounds like you have an underlying cause which is inflaming the bursa it its associated structures. 

I have bursitis & tendonitis in my shoulder, which they call impingement syndrome. I have finally had enough of the pain as nothing relieves it for long. Had two cortisone injections which relieved the pain for a week or so bu then it came back. Am having surgery in 5 weeks to fix this problem. I'm hoping it works.

Will let you know how successful it turns out.

Subacromial impingement syndrome represents a spectrum of pathology ranging from subacromial bursitis to rotator cuff tendinopathy and full-thickness rotator cuff tears. Management includes physiotherapy, corticosteroid injections, and, for some patients, surgery. Surgery is indicated in patients with persistent pain who fail a trial of nonsurgical treatment.