I second flip on this as well as adding in more grip type implements on top. Squeeze the shit out of the bar and try to go heavier holding things. Use fat bar type implements when you can. Buy a sandbag and start training with it without using handles. You can be creative as well and find rocks and such to pick up in a pinch grip or whatever's you can really. There are a ton of options out there.
On a side note, I like wrist curls, but only after a base is built from heavy carries, hammer curls, reverse curls, deads, rows, etc.