5/3/1 and real food would be a good start, and so would hooking up with like-minded powerlifters.
The "best" thing to do would be for him to aggressively lose fat, but I am of the opinion that any positive change will be beneficial to someone who has managed to get that heavy. If he changes nothing about his life other than becoming a person who trains regularly and with purpose, he will have taken a good step.
If he ever wants to be competitive as a powerlifter he will need to learn how to eat well and keep it up over time, or get ridiculously strong as a super heavyweight. And while your friend should be proud of possessing the strength he has, he should also keep in mind that a 505 deadlift is very strong...
...for a powerlifter who is over 200 pounds lighter than him. I'm not trying to bring him down by saying that, but it is easy for fat boys to walk into a commercial gym and walk out with a misguided notion that they are strong. Been there, done that.
But yes, barbells are good for both fat and skinny boys. No reason to put off training with them.