wris curls wont develop strength just overall fatigue of the muscle during the workout, the strength of your forearms comes from holding onto stuff for long periods of time, stuff like wrist curls... its not functional, functional training is the best way to develop strength, so, rack pulls... my number one favorite for grip strength... i can rack pull 210 without straps... grip doesnt fail, do carrys with the shrug bar, just hold a dumbbell... just hold anything... put a resistance band on the post or whatever, take a few steps back and open and close your hand to develop the gripping aspect of the forearms, worst comes to worst all you do is either drop the weight or the resistance band flicks against the wall