I typically do it 4-5 days before.
My dry brine mix is crushed juniper berries, black peppercorns, lots of salt, dill. I put it in a big plastic bag and keep it in the fridge flipping every day.
add saltpeter if you like a "pink" color.
Let is soak in it's own juices.
before i put it on the smoker, rinse it off with water and pat dry with a paper towel.
then put the dry rub that i'm going to use for the crust. Brown sugar, paprika, garlic, onion.
if i forgo the dry brine, it's the same dry rub but with salt added in the day of
I use the 1 hour of smoke, 2-4 hours of covered and last hour of uncovered on my weber.
i like #1 because it has that great jewish pastrami taste. but i go with #2 if i want more of a cleaner beef taste.