I don't know if this would truly be pastrami, but it is brined and smoked, just like pastrami which is corned beef that has been smoked.
I make a brine as follows for 1 gallon of brine: 1 gallon water pickling spice to taste 1/8 tsp of "pink salt" per pound of meat 1 cup canning/pickling salt 1 cup sugar
You'll need to decide how much brine to make, but I've been fine with 1/2 gallon for a whole sirloin tip roast.
I like to take a long fork and perforate the meat to aid in brine penetration.
Put the meat in the brine and refrigerate for up to 7 days. You may need to experiment, but you can tell when the brine has penetrated fully by the color change in the meat. If it is completely red/pink from the curing salt, it's ready.
Dry the meat off and cover liberally with black pepper and ground coriander.
Put on the smoker until done, somewhere between 135 and 150 depending how done you like it. I keep the smoker at 180 and use hickory for smoke.