Apart from heavy kettlebell swings there is another exercise that will give you a killer grip – its nail bending.
Once you find six inch hardware nails easy you can progress by snipping an inch off them with bolt cutters. The move on to bolts, screw drivers door hinge pins etc.
Admittedly I am new to the sport and have only bent a dozen nails so far. But they have all bent fully. I also have a “power twister” which the packaging says is 60KG torsion. A six inch hardware nail takes 280 – 350 lbs of force to bend but the power twister is much harder than a nail. I would say it takes 400 lbs of force (compared to the nails) so I don’t know where they get the 60KG from but its definitely much more.
Here I am bending a six inch nail.
Now my tendons are still getting broken in and boy – this really hurts like heck afterward. the first session it hurt all the next day – now I find it hurts for an hour or two after.