This thread feels a bit bodybuildish to me, but meh, at least we're talking forearms.
I tried lots of different stuff. The two best exercises that helped me put beef on my hands and forearms are
1) COCs
2) Load one end of a barbell, put the other end in a corner, step over the barbell (should be between your legs) pinch the plates on the loaded end and row away. Single best exercise to assist pinch strength IMO. Hell, I don't know why I ever stopped doing this. Gotta put it back in my grip work. My pinch sucks right now.