Eric, any training secrets for hand veins?

Well, I feel relieved that I don't have to revisit that whole topic, even if it is one of my faves.

I think one thing that was never really addressed is the "what are the best options"

From a low tech (most bang for the buck) standpoint I would suggest buying a small section of PVC pipe (something with an outside diameter of 2-3" would be ideal to start with). Not more than 6-12" would be needed, don't buy a 6' pipe. Then, simply run some rope or chain through the pipe, hang weight on the rope/chain and you have a great grip tool. You could also drill a hole and mount an eye-bolt or whatever, but... not necessary. This kind of gripping works the fingers and thumb in a static state. It will have good carry over to holding onto a normal old bar. Keep in mind that you want to grip your pipe section like a prize-claw thing. Don't wrap your wrist under it, that has nothing to do with hand strength.

There are variations of this, of course. You could use an old baseball or softball and drive an eye hook into it from which to hang weights. Or you could nail a couple 2x4's together as a pinch grip tool.

Grippers are fun, and lord knows I have spent a good amount of time working on them, but the grip strength developed is incomplete as it never hits the thumb, and the carry over to barbell lifting isn't great.