I’m going to assume little knowledge of targeting blackfin so please don’t take it the wrong way if this is too basic.
The best area to start is the SW banks east of charleston, the break there runs from the SW banks into the Georgetown hole. You can get lat lons for those pretty easy on line. If you don’t have them reply back and I’ll pull them off my machine and post them.
Fish from 165ft-300ft depths, find ledges and drop offs, there are many in this part of the ocean
For blackfins cedar plugs work well and don’t require re-rigging, usually. They have painted ones but I find the pre-rigged plain wood ones work best.
The other lure of choice is a sea witch ballyhoo skirt. Mustad 7766 hooks are the best for sure.
https://www.youtube.com/watch?v=zjI7sSAt4zw
Carolina Lures is the original one but most people like the Blue Water Candy now. Use some bright and some dark colors. Don’t get sucked in to one color they will bite different things depending on the day.
Rig them on 60lb to 100lb fluorocarbon. I use 80lb.
https://www.youtube.com/watch?v=gHt7lyQOyeM
Tuna wahoo and dolphin will bite these things. Troll 5-7 knots.
Pull your outside lines way way back. pull everything else our of the white water in clean water.
A lil’ bubbler behind a set of boone birds is a great teaser.
This is standard fare for around here. I have not had as much luck with the islander lures for tuna over the years. They are expensive. you can order sea witches by the boat load online for cheap.
If you want to get super fancy go with wind on leaders using these swivels in place of the snap swivel.
https://www.amazon.com/SHSB-03-5-Heavy-Swivel-150-Pound-5-Pack/dp/B0007RL3FM/ref=sr_1_1?ie=UTF8&qid=1522425490&sr=8-1&keywords=spro+swivels+150+lb
Crimp the floro leader to the spro barrel swivel and then tie the rig and leader to the main line using this knot, you’ll have to pass the witch and leader through the loop to make this knot but after you do it a few times it’s pretty easy:
https://www.y