To perform any exercise with proper technique you need to hold the weights with solid grip but for holding it for too long you need strong forearm. Our forearm involves in each type of weight workout so automatically it gets stronger with other parts of the body but that is true for the beginners as you start lifting heavy weights your forearm lag behind biceps or triceps.Grip plays important role when you perform DeadLifts or Pull-ups. There are some exercise which helps in building strong forearm.
Farmer walk does help in building strong forearms although its a compound exercise. Grab couple of dumbbells in your hand and try to walk with it like you normally do.
Another way is to grab some weigh plates and try to hold them with strong grip try to squeeze the plates as hard as you can while still holding it in your hands.
Another workout that is best to test your forearm strength is standing rope forearm. Grab a plate and a rod and attach both with the rope then try to scroll the rope on rod while stretching and keeping your arms parallel to floor.