Tim, I've been captain for two current IGFA line class world records for my wife (95 lbs on 8 lb and 46 lbs on 6 lb), but these are West Coast fish. Still, the methods used should still work.
Near shore threshers (water depth 200' or less) demand different methods than offshore threshers. The nearshore fish are typically juveniles ranging from 30 lbs up to 150 lbs. Female threshers first start breeding at 3 years and about 150 lbs. A 150 lb thresher will have a fork length of about 62" to 63". The most difficult part about fishing threshers, either nearshore or offshore, is finding them. Once we find them (looking for feed pushed to the surface), we slow troll nose hooked sardines or mackerel of 10" or less. We will use straight 100 lb mono leaders of 10' to 15' (max length for 20 lb and under per IGFA) and Mustad live bait hooks. We attach 2 to 3 oz torpedo sinkers to the leader using rubber bands. I attach main line to the leader using a padded albright knot. For record attempts, I also use about 15" to 18" of 69# single strand wire haywired twisted to the hook and a welded ring or a 250 lb SPRO swivel (very tiny). The best trolling speed is 1.5 to 2.0 knots. Dropback is a matter of preference. I've done as little as 30' and I've seen friends drop back as much as 150'. Quiet engines are better. Four stroke outboards are ideal as they slow troll quite well and are quiet. I'm trolling from a 20' center which has a Volvo Diesel in it. I have to throw out a drift sock to slow my troll speed from the normal 2.5 knots down to 2.0 knots. Preferred reels are Shimano TLDs or Trinidads. On the TLDs you have the clicker on and the drag lever pushed up just enough to stop line from going out. On Trinidads you use the adjustable clicker to accomplish the same. The thresher may tail strike the bait causing a zip on the reel and then come back. If you can, put the reel in freespool and pull the boat out of gear, causing the bait to sink out. Threshers slash through a school of bait and then come back around to eat what sinks out. At this speed, threshers will also just mouth strike the bait and take off like a freight train. In this case, simply push or flip the reel into gear and take up chase. Mouth hooked threshers will jump and they come in great condition for release fishing. You can simply take wraps on the leader, pull and break the hook. My wife's 6 lb record was weighed live at the boat ramp (1 mile from where it was caught in Long Beach Harbor) and released. The fight is very similar to my recent night tarpon experience in January off North Miami Beach.
Offshore thresher fishing is different in that the fish are bigger (to 500 lbs here on the West Coast) and we also incorporate the use of downriggers at the thermocline (80' to 90'). We troll a bit faster (2.5 to 3.0 knots) and we will used rigged dead baits or live baits (mackerel). We also run rigged mackerel behind a 16 oz Bait-O-Matic on flat lines. Our typical pattern is two flat lines and one
Downrigger line. You find them and they will find your baits. Since the trolling speed is so slow, it's best to hunt for bait balls on the meter at higher speeds before putting your gear in. A good network of eyes on the water will greatly minmize your hunting. Typically we use 50 lb tackle and above because these fish will dog you deep. Most of these fish will be tail hooked.
If you have more detailed questions, please feel free to e-mail me. Our season will get going in another month and a half as the water temps start climbing above 60. Ideal temps are around 64. We will be targeting records on 4 lb (Men's and Women's) and hope to get the first thresher on the Fly. We will also be working with Scripps to implant arichival tags on threshers.