How would a level 19 feral druid go about killing a level 19 hunter(each spec) in a wsg?

With great difficulty I'm afraid. At that level, Hunter twinks rule in BGs.
The best I can offer is to just practise until you find tactics that work for you, but as I say, a good Hunter twink at level 19 will always have the edge in a BG.

p.s. with the latest patch you can earn Conquest points in normal (i.e. non-rated) Battlegrounds, so do as many BGs as you can so you can purchase good quality PvP gear with Resi stats (Resilience is a must for BGs).
p.p.s. If the Hunter is a BM (BeastMaster) take out the pet first!