Resistant spring grips(No idea what there called)but build your way up to a 100 reps a set and ten sets throughout the day,Also flat dumbell wrist curls.When i was seriously training my forearms were very good and helped my grip for Deads.
i was thinking of doing something like this:
hang board - 5-8 sets of a few reps of 5-10 second holds
sand extensions - 5 sets of reps to be determined once I've tried them
static holds - 3 sets of double overhead, 5 sets of hook grip(maybe with snatch width grip sometimes?), 3 sets of mixed grip. reps 5-15 seconds.
sand grabbing - 5 sets of reps to be determined once I've tried them