These two videos will tell you everything you want to know.
YouTube - Gunsmith - How to smooth double action trigger pull on a S&W
YouTube - Gunsmith - How to smooth single action pull on S&W revolver
You don't really need the tool to remove the rebound spring but it helps. I made my own out of some 0.186" brass rod. If you take the side plate off make sure you use a proper hollow ground bit or you will ding up the side plate screws. If you don't have a proper screw driver find one whose blade matches the width of the screw slot in the head of the screw as closely as possible.
Photos of homemade tool attached.