Corsair G5 Guide: By Jekyll

Testimony Farming
(I-7) of Caedarva Mire's first map is the best place to farm this from Lamia Fatedealer. Even though there are other undead surrounding them, they are very easy to pull near the zone since they aggro by sight unlike the rest of the mobs there. I was 1/4 on Testimony and these have a respawn time of 5 minutes as opposed to the 2 Merrow Icedancer's 15 minute respawn time in Arrapago Reef. 
Equipment
Main: Fire Staff (+1 Optional)
Sub: Fire Grip
Ranged: Matchlock Gun
Ammo: Steel Bullet
Head: Corsair's Tricorne
Neck: Peacock Charm + Opo-opo Necklace
Ears: Vision Earring/Drone Earring
Body: Corsair's Frac
Hands: Deadeye Gloves
Rings: Behemoth Ring +1 (+1 Not entirely necessary)
Back: Amemet Mantle +1
Waist: Precise Belt
Legs: Jaridah Salvars
Feet: Corsair's Bottes
Items Needed
Poison Potion x1 (To avoid being slept by Light Shot)
Sleeping Potion x4 (To store TP to 100%, obviously this is to be used with the Opo-opo Necklace)
Sole Sushi +1 (Ranged Accuracy +16%, this will ensure you don't miss on Slug Shot)
Selbina Milk x1 (Will prevent you from being dispelled by Dark Shot)
Blink Band (Recommended in case the Captain gets near with his sword, not needed but it may save you)
Icarus Wing (For the 2nd Slug Shot
Step By Step
1. Eat the Sole Sushi +1
2. After equipping the Opo-opo Necklace use 1 Sleeping Potion
3. Hunter's Roll to a number you're comfortable with
4. Use 3 more Sleeping Potions 
5. Chaos Roll to a number you're comforable with
6. Use Blink Band if you have one and/or remember to swap out your Opo-opo Necklace
7. Use Selbina Milk and Poison Potion
8. Get within range (Seems obvious but this can mess up your TP)
9. Slug Shot
10. Use and Icarus Wing and Slug Shot a second time (This will Skillchain Reverberation)
11. Fire Shot
12. Fire Shot -At this point in time he should give up and you should be left standing, if this is not the case use Wild Card and hope for the best, which could be either TP to Slug Shot again or having your Quick Draw reset to Fire Shot again.
Side Notes
Your Marksmanship Skill should be capped @ 228 or close to it, otherwise don't even attempt to fight.
The Captain is pro with the sword and hits very hard with it, try your best to not get near him if possible, keep it a ranged fight.