Every pit master has secrets. Eddie Brown at Off The Bone in Forest Hill, the Dallas-Fort Worth area’s top-ranked barbecue joint, is no different. What kind of wood do you use in your smoker, we asked Brown on our recent Tarrant County tour. “Yum Yum,” he said. What’s that? “Can’t tell you, it’s a secret,” he said. “But it starts with a ‘P.’” Pecan. Brown smiled and nodded his head. He said he mixes pecan with oak. And he kept that proportion to himself.Off the Bone BBQ, 5144 Mansfield Hwy, Forest Hill. Open Tuesday to Saturday, 11 a.m. to 8…