I've been focusing on grip strength lately and trying to eliminate any holes in my routine (i.e. grip strength, calves, specialized core training) and I have found my new favorite exercise. Plate pinches and step-ups. Together. So simple, so easy, but so, so hard... My hands are blowing up like balloons. I do these with a partner to keep me from going over the front of the bench by just putting his hand to my chest so I can lock my calves at the top of each rep. I also have been rope climbing instead of doing pull ups, and I recommend for anyone who is getting tired of pull-ups to get a rope and climb it.
I found towel hangs help, too.
heavy double overhand stiff leg deadlifts are no joke for unreal grip strength