Richie,

Thanks for the great question!

My suggestions would be the following:

1. Nothing carries over to support grip strength more then thick bar training. This can be done with an axle. Cycle in an axle into your pull training periodically. If you don't have an axle;

a. Go to the junkyard and get a thick pipe - take along a 2 1/2 lb plate for sizing
b. Wear winter gloves while training on the olympic bar, looks funny, but f*ck it - IT WORKS!
c. Wrap a towel around the bar and grip and rip.

2. Build static support endurance with timed rack pull holds. Heavy rack pulls held for time double overhand (pronated) grip will have a big carry over to your standard reverse grip deadlift strength.

3. Don't forget to CHALK BACK OF YOUR POINTER FINGER! When you're not hooking, this is the anchor point for the thumb!

4. Start your pulls with your wrists cocked. Why would you do this? Because it distributes the load across the hands and engages the forearm musculature, instead of just centralizing the effort in ONLY your hands. Longevity wise, this will have a HUGE CARRYOVER to your overall support strength.

5. You are right on track with the hex head holds, but don't forget your plate pinches and blockweight training. Remember - blockweights have a huge carryover to OVERALL hand strength.

Keep working brother, you're doing everything right!

,
Jim Smith