Hi Damien,
I do a slow boat Swains trip every 18 months or so with a group of guys from work.
I caught my first GT there on a Nomad 80 gram stickbait. There are plenty to catch, and in all sizes, you just have to get away from the bait fishermen and chase them.
As with all GT fishing the reef edges where current is pushing against are prime places. Look for eddies, bombies and any points exposed to the current, and fusilier schools.
A balanced group of lures including different sizes of poppers, floating and sinking stickbaits will do the job.
I am not concerned too much about colour, just get your lures action right.
Oh and make sure you upgrade your terminals to decent hooks on Owner/Decoy rings.
Don't worry about the weather, you can't change that, its just luck. On my last trip to the Swains we had 3 days of 30 knots and still caught fish, 40 Knots for 18hrs on the trip home left a bit to be desired though.
The best bit of advice I can offer though is to constantly try different things if the fish aren't biting.
Jig metal for Mackeral, cast poppers for trout, plastics at bommies, fish deeper water, in current, out of current etc, etc.
Its a long way to go not to make the best of the trip. It is too easy to come home and say the weather was bad or the fish were off the chew. Something will work, if you perservere you WILL catch good fish.
And one last thing.... its not much fun fishing high drags out of an unstable dory so be careful.
Hope this helps,
Ken