I've been doing this upper body workout twice a week:
A handful of sets of hand / wrist / grip / forearm exercises: mostly finger pushups against a wall, finger extensor pushups assisted with legs, wrist curls, reverse wrist curls.
As a finisher, I do a farmer's walk.
Goals are strength and mass, and to bring up my hand/wrist strength and endurance, which is a weak spot. I've basically been doing whatever extra hand/wrist work I feel like at the end of the workout, without a set-in-stone plan, but I have been pleased with the results thus far.
My question: How long/far/heavy should I be going? Last time, I took the dumbbells out of the free weight room, for a loop around a 200 meter track, and then back into the room, which took 3 minutes. Is this good, or should I be using a weight I can only carry for 1 minute, or 40-80 seconds, or 75 meters, or some other magic figure?