Any thoughts on how to effectively play Bristleback please?
Bristle's one of my comfort heroes, I normally play him as a greedy offlaner. Normal build I go is Tangoes, Salve, Stout Shield, Mango, Ironwood Branches, then Treads -> Magic Wand -> Vanguard -> Echo Sabre -> Basher -> Abyssal. From there I like Octarine, because Octarine goes so well with spamming your skills/Warpath getting more stacks/decreased cooldown on basher/echo sabre procs, but it's definitely super greedy. Blademail is good, as is AC. If you prefer to get your team to push with you rushing Greaves first is ok, but I think the other item build is generally better.
General tips: Bristle's pretty good at ensuring you get decent CS even in the offlane. Bristleback passive from level 2 onwards makes you pretty hard to kill, and you can CS relatively safely even with just 1 point in Quill Spray. At level 3 I normally have 2 points in Quill Spray and one in Bristleback. At 4, if I think I can get a kill I'll get a point in Goo, otherwise I'll get more points in Bristleback. As a rough guide: if you manage to get 2-3 quill spray stacks on the enemy, have a healthy amount of mana, and they aren't backing up, don't have a mobility skill like blink, and you have boots, you should be able to chase the guy down with goo and quill sprays and kill him. Make sure to account if the enemy has stick charges from you spamming your skills though!
Once you get Wand/Vanguard, you're pretty tanky, so try to get your team to fight with you as the frontliner. Bristle thrives in long, drawn out engagements, so try to spray the enemies a bit, look like you're backing up/draw the opponents back into your team, turn back around, etc.
Things to look out for: Heroes that build Silver Edge (losing Bristleback passive hurts and throws off your ability to calculate how aggressive you can be), heroes that make you face them (i.e. Axe and LC), and heroes that kill your mana (KOTL, AM, Invoker, etc).