I have a 642 that I swapped out the Hammer Spring and the Trigger Return Spring with a Wilson Combat spring kit. I like my Smith and Wesson revolvers as some of you may know. These are easy to change in about a half hour if you go slow. I have a Rebound Spring tool by Wheeler Engineering but it does not fit the aluminum frame guns, only steel.
I am running the 8# Hammer Spring and a 14# Trigger Return Spring.
I hate to say it, but searching on YouTube for videos is easier than trying to type out everything to describe all that's involved in changing the springs out.
I only changed these out because I carry the gun and my wife has to be able to pull the trigger if I cannot. She has weak finger strength for heavy double actions. The difference is easily noticed after you change them and she could pull the trigger just fine.
The parts were less than $10. The other alternative is to dry fire the gun a lot to smooth the action up.
(The pics or it didn't happen)