Weak grip? Try out rope pull ups to develop your grip strength and your forearms.
All it takes is two towels (or a thick rope if you have it). Hang the two towels on the pull up bar where you would normally position your hands. No need to go crazy with the width, shoulder-width or a bit wider than shoulder-width should suffice for this exercise. Grab onto the rope and start doing your pull ups. You want to be gripping hard and really squeezing the towels. Make sure the towels won’t slide off the end!
Like with regular pull ups, an overhand grip (palms NOT facing you) will focus more on the lats, while an underhand grip (palms facing you) will focus more on the biceps. Alternatively you can use a neutral grip (palms facing each other). An overhand grip tends to strain your wrist quite a bit, so make sure you twist and rotate your wrists as you pull up. You want to be turning your pinky towards you as you pull (we call this rotation supination).
Oh yes, your forearms are going to be pumped to the roof; they should be burning pretty nicely too the morning after.