BBQGRAIL helped me out last Saturday when I did mine (although mine was a store bought corned beef brisket that I soaked overnight and rubbed with a recipe like the one above). He recommended either steaming the whole pastrami after it cooled completely in the foil by putting in the oven (covered) in a roasting pan on a roast rack with about 1" water in the bottom of the pan. OR he said that he likes to steam the slices in the oven every time he carves.
I didn't end up bothering with steaming
....I diced for hash and then just sliced for sammies, but it WAS a bit tough.
Sure would love to hear how this turned out for you. I will likely do this very soon.