As smoke from the oak-burning barbecue pits swirled around his head, Nestor Laracuente lit a Marlboro Red, inhaled hard and puffed out his own cumulus cloud. A pitmaster at Hometown Bar-B-Que in Red Hook, Brooklyn, Mr. Laracuente says nicotine and heavy metal help him through the marathon graveyard shifts he spends monitoring the combination of heat, meat and smoke that it takes to produce extraordinary barbecued brisket.