You want to cook tri-tip like a big ol' steak. Smoking is not your friend with
this cut. Use what I call a "Red Neck Sous Vide" method, which is also
known as "reverse sear". Cook the roast indirect until it hits about 110*
internal, then sear it over direct heat (400-500*) for about three minutes
per side, to a finished temp of about 125-130*. You're looking for a
beautifully dark, but not charred crust.
Let the roast rest for at least 10 minutes, and then cut it across the grain
1/8" to 1/4" thick.
All you need for seasoning is kosher salt, fresh ground black pepper, and a
little granulated garlic.
I hope this helps,