my family is from california, and tri tip santa maria style is one of my favorite things to smoke.
nice thing about it is that it is a quick smoke... generally less than an hour, so it works when the wife says "I invited the neighbors over for dinner tonight. can you smoke something?"
I use a rub of equal parts table salt, granulated garlic and dried parsley.
get the fire going for a short smoke (325-350 degrees). I accomplish that with my weber by leaving all the vents wide open and leaving the water pan empty. red oak is the traditional santa maria smoke wood, but I use mesquite most of the time.
twenty minutes in the smoker before the first turn, then monitor it until the meat gets to 125-130 degrees (usually another 20 minutes). I then remove it from the heat and let it rest for 15-20 minutes under a foil tent.
slice it thin, and serve it with good fresh salsa, a salad and beans. open a good california pinot. voila, california barbecue.