To train grip if you can find something to hang from grip it with palms facing away from you and bring your legs off the ground just hang there. Do it about 4 times for as long as you can and don't fix your grip when you start to slip this will allow for fingers to train in strength. Other things you could do are grip trainers or whatever they are called http://pi.b5z.net/i/u/230085/i/Hand_grip_hand_grippers_apt.jpg
those things haha
Another one of the oldschool ways to train grip is to grab the two largest plates you can and hold them by squeezing them together from the top. Then if you desire, you can raise your hand out to shoulder length and strengthen your entire arm.
Dumbbells work too, though the weight you can use may be limited by the size of your hands.