The inverted row isn't just for beginners. More advanced lifters can use it to build massive forearms and crushing grip strength. Just use a thick bar or Fat Gripz attached to a regular bar.
Set up a thick bar in a rack or use Fat Gripz.
Get a good grip on the bar, pull, and pause for 1-2 second count at the top.
After 7 or 8 reps, you'll really feel it. Ramp it up by wearing a weighted vest if needed.
A 2-kilogram discuss traveled 140 feet through the air and landed in Dan John's skull. After that, he "rested" for five months. Now he has some interesting ideas about rest periods in general.