For threshers, most people use a somewhat specialized rig. It is much like a sliding live bait rig, but majorly beefed up. Instead of a snap, what is usually used is a wire slider or a "non return slider", upon which the leader is attached. For the leader, usually 4-10 feet (depends on water conditions) of 60-100 fluoro is used, with lines on the heavier end being preferred. Sometimes a float is attached to the leader at the slider to keep the mackerel at the surface. To anchor the mainline, a 5-6 oz sputnik style sinker is usually used. As for the mainline, a long shock/rub leader of 60-100 lb mono is used, as to prevent damage from the shark's rough skin. Meanwhile the mainline is usually 30-50 lb mono or 65-80 lb braid. With this rig, the mackerel is mostly free to swim around in a circle with the radius of your leader, so keep your distance from other anglers.
This website has tackle (though at a somewhat unreasonable price) and the pics will help guide you if you choose to make your own rigs:
http://terrafirmatackle.com/shop/