Old post, but I'll chime in.
Farmers walks at the end of your workouts, something like every 3-4 days. Grab the 150lb DB's or the heaviest your can hang on to, and go for a walk around the gym. Make sure they're heavy enough that you drop them somehwere in your walk. Make at least 4-5 laps. The final lap should be a struggle, re-gripping the DB's every 10-15 feet or so. I did this religiously in high school and college. It's why my forearms at one point where bigger than my biceps and also why I pulled 585 with no straps my senior year with just chalk and a belt. I actually don't do them any more because my forearms got TOO big.