Wrist curls, barbell holds for time, and dont use straps until absolutely necessary. Your grip will improve. Straps have their place but you can do more without them than you think. There are times when I just dont want to think about my grip, so I use straps and the next week my grip is better from the "rest."
I dont know that crushers do that much but thats just my opinion. You should talk to thewickedtruth, he's a grip monster.