Don't dismiss the PC master action job. My 625-10 has had one. Most people that dry fire it think it's about 6-8 pounds. The old trigger pull gauge measures it at 13-14 pounds. Smooth helps a lot.

Don't change the factory mainspring - the replacement is only ½ pound less. You'll do better by breaking and smoothing the edges of the hammer strut. You can also change the rebound spring from the factory 18 pounds to 15 pounds with no effect on reliability. Some people go lighter - I wouldn't. Most of the smoothing benefit comes from smoothing certain surfaces/edges of the rebound slide. If you don't know how to do that, leave it to a pro since you can mess things up by "smoothing" too much.

Buck