You cook it at "low" heat(220-250) until it is within 5-10 degrees of the doneness you want, I go 110ish degrees internal. Then you pull it off and get the grill(I have a green egg so it gets HOT) as hot as you possibly can, then sear it 60-90 seconds each side. Rest it for a few minutes while you prep/plate everything else.
You *can* do the reverse portion in the oven and still get alot of the benefits. If you do it on a charcoal powered grill you get alot of smokiness during the low temp portion.
I guess Facebook is good for something, there was a video of this method on there last week.