I would not see the reason to use the fat grips for this kind of training. I would seriously advise some sort of periodization program for it while being sure to focus heavily on the wrist development with wrist curls, reverse wrist curls, and sledge hammer work. But most importantly curl the way you are going to have to curl. Then add on from there. I would no deviate to much from the way you have to actually work in contest. Most arm wrestling programs will be similar to this.