I think the best way to train is to basically run through the show on your event day once per week. I does you no good to be able to do one of the events when you are fresh if you can't do it on contest day after you have done several other events. There is no better way to train than training for what you want to do. Strongman requires a special kind of conditioning. I would have a hard time running a good time in the mile, but I feel doing the events regularly (I do no other GPP or cardio) keeps me in pretty darn good shape for doing events (i.e. 30 sec to 1 minute bursts).
I think it also helps to hit your entire body multiple times per week. I do not subscribe to the train one body part, or group of body parts, each workout. Rather I hit my entire body in different ways each workout. Powerlifting style one workout (e.g. wide box squats, 3 board, abs, calves), OL style another (e.g. power snatches, front squats, overhead jerks); assistance stuff (bodybuilding like) another (e.g. dead for reps, abs, calves, adductor/abductor machines, lats), and strongman events on another day. Grip is typically worked multiple times during the week as well.
On heavy stuff, I almost always wear a belt. To me, it is not worth the off-chance that I will tweak my back doing an 800 lb yoke or whatever and be out of commission from training hard. Plus, given the amount of volume I am doing, I cannot afford to completely smoke my back on any one exercise during the week.