The J-frame is descended from the older I-frame, and only a little larger and heavier. The I-frame in center fire calibers was available in .32 S&W Long and .38 S&W. With these recoil was quite manageable.
I point all this out because today folks are in affect using the same platform, but chambered in .38 Special and even .357 Magnum. The result is recoil that is (as you discovered) painful, abusive and likely to help flinching develop. None of this is conductive to improving marksmanship.
It may be argued that .32 S&W Long and .38 S&W are inadequate for serious self-defense, which is a matter of opinion, but in any case if one believes that the more powerful cartridges are necessary they should do themselves a favor and move up to a S&W K-frame or Ruger SP 101. Both the condition of their hand(s) and marksmanship will likely show improvement.
Old Fluff speak many truths.
However, I've found the SP101 to be on the heavy side for me. It might work well in an IWB holster, but I prefer a set of Barami Hip Grips for snub revolver carry as they are so compact and don't print much at all. I'm a smaller individual and have had a tough time with printing. The Baramis are the best thing for me yet.
I love shooting my 642-1 at the range. The thing is just a hoot, yes recoil can be sharp with some loads. I have found the Winchester 130 grain FMJ white box target loads from Wal-Mart to be consistent, fairly low recoil, and in general very nice to shoot. I buy some when I can find it. It's worth a try, it is IMHO a great practice load for .38/.357 J-frames.
I haven't shot my J in a while, and last week at the range I did and the results weren't so hot! I kept thinking to myself "I remember having much tighter groups last time!" but last time probably was too long ago. These little guns are especially sensitive to degrading marksmanship, and as shooting is a perishable skill, I'm afraid I'm not as good with my J-frame as I used to be. But, I'm planning on getting back to where I once was.
OP, I've found the proper grip and a nice firm hold go a long way in reducing J-frame pain! I feel you on that one. The web of my hand invariably gets sore after a session with Lil' Jay.
To help, I recommend one of the grip strengthening exercise tools. These can really help you control the gun better, reducing fatigue and pain. I have the "grip master" brand (I think) in the "red" model, which is intermediate strength. It has helped me I think both in steadiness and grip strength.
Might be worth a try!