1) Often I will start the fight with Double Shot and Camouflage. I keep Hunter's Jerkin +1 on me for it, and I actually have three Camouflage merits and will be capping it once I take down some Unlimited Shot merits. I just sit back and shoot until Camouflage wears off, then use weapon skill. Using Camo whenever it's up helps a whole lot with enmity management.
2) I've always had capped Stealth Shot but it has been more significant than ever with this gun. Often I will just shoot for DPS if Stealth Shot is even a full minute away. It sort of defeats the purpose of a 5-hit, but you're still dealing quicker damage than other ranged weapons, and you won't get killed for using your WS.
3) Enmity Down builds - again something I always used but is now vital. Enmity- is more accessible than ever now with the new items and I cannot wait to get my hands on some items like Praeda Gauntlets and Sylvan Scarf for this purpose. It makes a very significant difference and I usually Slug Shot in a WS/Enmity- hybrid build whenever Stealth Shot isn't available.
4) Dragoon subjob. People gave me all sorts of funny looks when I started to do this, but they quickly recognized the potential when I crushed them on parses and never died. Having High Jump to cut 25% of your hate every 3 minutes means you can use your most damaging abilities, then High Jump the hate away. I'll usually wait til High Jump is ready, Slug, Barrage, Slug (fully expecting to take hate in the process) and then High Jump. I've never had a mob continue attacking me after a High Jump. The only problems I've encountered have been when a mob prevents me from using High Jump (Odin's stun move, Farruca Fly's enparalyze, etc.) and then I get messed up pretty badly lol. Subbing DRG doesn't add any offensive benefit whatsoever, but with a gun like Spitfire you hardly need Meditate, Sekkanoki or Berserk. You could also sub NIN, but I like DRG since it gives me a little more control about when I step over the hate line and step back.