Breast/shoulder pain was one of the first symptoms I had before being diagnosed with TOS once the pain/numbness moved down to my hand. I tend to steal my dog's toys to use for trigger points. My favorite one to use for the chest is this one:

http://www.petsmart.com/product/inde...AvailInUS%2FNo

Don't laugh, I think it works great. I put the tail end against the wall push my chest muscle (just below the shoulder joint and next to the arm pit) into the nose part. I hold onto the body of the toy and move around until I find the sore spots. I use the regular tennis type balls for all the other muscles, but find them awkward to use on the chest.