I have never had a problem with my grip. It always feels pretty strong and I only miss pulls because my technique goes to shit with max weights. I do train the shit out of my hands though. Not to say these exercises are the 'x-factor' in grip training or anything but having an 800lb+ bar in your hands and it not feel heavy is doing something right.
-Double Overhand Fat Bar Deadlifts- I either work up to a 1rm until grip fails or a 5rm until grip fails. There are brutally effective. Actually, the more I do these, the more I realize that the weight on the bar is right around 50% of what I pull in a meet.
-Plate Pinches/Blob Pinches- either pinch a bunch of 10lb plates together for time or max weight or (this is one of my favorite exercises ever) take an empty db handle, load one side with the pinch width you want (I usually use 5 plates because it sucks) and then progressively load the other end with more weight. As this weight goes up, so does the comfort of your pulls... for most people anyway.
-Captians of Crush-Close and HOLD- just closing them did nothing for my grip strength. Closing the heaviest gripper I could and holding it for 8 seconds made me feel like I was going to throw up through my finger tips.
Everything else I have tried doesn't really do anything for pulling. Any variaiton of pinching works very well and you can get very creative with the exercises.