I am by no means an expert but I have used homemade and storebought corned beefs many times to make pastrami. Pastrami is simply a smoked corned beef with a black pepper heavy dry rub. It's delicious and will be one of your favorite smokes (it's one of mine at least).
My recommendation would be to soak it at least 24 hours in cold water to desalinate it. Store bought tends to be really salty. Then dry it off, and apply this rub:
4 tablespoons fresh coarsely ground black pepper
2 tablespoons coriander powder
1 teaspoon mustard powder
1 tablespoon brown sugar
1 tablespoon paprika
2 teaspoons garlic powder
2 teaspoons onion powder
You could coat it with a little oil or mustard to make the rub stick. I usually let it sit in the fridge for a few days before I smoke it.
Smoke it anywhere between 225-275 with a lighter wood... I like apple the best. Bring it to an IT of 195 or so. Now this is the key. Resist the temptation to eat it all at that moment. Haha throw it in the fridge for a couple of more days and then steam it back up to an IT of 203. It will change your life!!! Haha here's a link to the first one I did:
Disclaimer: I don't take credit for this recipe or technique. Just a combo of a bunch of techniques and recipes I learned on this and other sites. Hope this is helpful and good luck!