Couple of thoughts from a doc that specializes in managing these kinds of patients.
1 - Mechanics of CPR - Just listen to pmedic920. He nails the technique, and the updates.
2 - Outcome of CPR - There are a couple of things that affect the success of CPR. #1 is there an easily reversible cause. If someone's heart stops because blood flow has been completely obstructed, no amount of CPR will help, unless the obstruction is relieved. If there is an isolated, reversible cause, like an impact induced dysrhythmia, CPR can be very effective. If you are doing CPR because of a car accident or other trauma, you're likely to have a bad day. #2 Time to initiation of CPR. This is way more important than duration of CPR. In my environment, where I can measure the output of the heart in real time, and thus evaluate the quality of CPR in real time, CPR duration of 15 to 20 minutes still tends to have remarkably good outcomes. Part of the reason is that I now deal exclusively with witnessed arrests, with immediate CPR, and immediate defibrillation, if necessary.
3 - Thoughts on what is going on with Hamlin. I wouldn't read anything negative into the fact that he is still intubated today. There are a number of reasons we leave people intubated. It is possible that the institution he is in still does targeted temperature management for these cases, and that requires a sedated and intubated patient. Sure, he could be requiring intubation because of the worst, but that is less likely.
The chances that he actually stopped breathing, on the field are somewhere between none and zero. Breathing is one of the last things to go when someone dies. He may not have been protecting his airway, but he was not down long enough to stop breathing, unless the collapse was from some sort of head injury, suffered earlier in the game.
Pre-existing condition - There are multiple pre-existing conditions that can leave the heart more susceptible to electrical disruption. My best friend has a rare, genetic condition that was discovered after he had a v-tach arrest on my boat. For those of you, like Pmedic who get it, his heart rate was over 200 for 30 minutes before we could get the helicopter into us to defibrillate him. That should be lethal, but somehow he survived without brain damage. Of course he is a cowboy with no brain to start with.