A support Bristleback guide mainly created to lane with a heavy physical damage dealer ranged carry, preferably a Desolator buyer to stack negative armor on your enemies.
Your laning stage goal is similar to most other strenght pos 5 heroes like Tusk or Ogre Magi, to tank as much damage as you can and help your carry get early kills with you stacking Goo on enemies. I highly recommend you go for a kill when the first waves arrive if the enemy team is missing sources of dispel.
Your mid-game stage job is to roam back and forth lanes like your pos 4, helping your team and when possible, farming your aura items for later team fights.
Late-game strategy is playing as your teams' second pos 3 initiating and tanking fights but be careful you might be way more squishy than a normal pos 1 or 3 Bristleback. Your main goal in team fights is being targeted by the enemy team and stacking Goo on them by being attacked since your passive now stacks Goo instead of Quills.