If your training grip for Farmers:
farmers holds for time
Farmers walks for weight
Farmers for distance
DB farmers/holds, as suggested, are a killer.
fat bar holds
Place fat bar over power rack, hang for time, dont use false grip, can also be done on reg bar, chin up
dont use straps, ever.
---all the CoCs, grippers, pinch grip stuff i'm sure doesnt hurt, but never did anything for my static grip strength