Unscrew the sideplate on your J-frame, and take a look. You will notice a spring inside the grip that actuates the hammer, and a spring inside the transfer bar behind the trigger. The spring in the handle is responsible for the stiffness of a double-action pull, so slackening it a bit will reduce this. The spring in the treansfer bar controls the stiffness of the single-action pull, slackening this will have the same effect for the SA pull. You will also notice (if you remove the parts. don't do it unless you know what you're doing, they're difficult to reassemble, trust me) that some of them have rough corners and rough surfaces. Polishing up these parts will make the trigger pull feel smoother.
Obviously the springs can only be slackened to a point, too loose on the mainspring and the gun won't fire, but the little bit that they can be will make it easier to shoot.
Smoothing out the internal parts, and reducing or stiffening the springs (per your request) are standard parts of a "trigger job".
A competent gunsmith should be able to do this with no problem, but I would ask for examples of his work if possible. Do that with any gunsmith work you request.