I don`t know if you`ve "pulled the trigger" so to say on reducing the trigger pull but I too have recently attempted to lighten the pull on my 686. (see threads)
Bottom line...you can lighten the pull somewhat but you`ll not get the pull that you`d like to have in double action and retain reliability with all brands of ammunition. I went with the Midway Reduced Trigger Pull kit and upon trial and error found that the 13lb rebound spring and the STOCK mainspring was what I needed to assure that all factory ammo would fire reliably. Initially I went with the 13lb rebound spring and the reduced power mainspring. The reduced power mainspring would not ignite Hornady Leverevolution ammo which is a requirement of mine since I also have a Marlin 1894c rifle chambered in 357/38 special and I like the common caliber that they shoot. If you handload then you may be able to find a primer that it will reliability shoot with the reduced power mainspring but since I don`t reload (not yet anyway) that wasn`t an option for me. Concerning the rebound spring tool that you can buy I`m sure it would be a help but isn`t necessary to change the spring. The Miculek video on YouTube is a great help and makes it fairly simple to replace. Good luck in your endeavor and if nothing else you`ll learn a great deal about your fine weapon.