Carl,
The biggest secret in my oppinion is not to use steel trace. I find couta generally go for the head of the bait/lure and Natal Snoek go for the tail, so there is no need for wire, use a 5' long fluoro leader between 12 & 20lb. You can get away with the heavier fluoro in dirty water, but once they hit the clean water you will have to go down to a 12-14lb. Another thing is to re-tie every now and then as the line can get nicked in the fight, and only use the Rapala knot, it gives the lure a lot more action.
You need a reel with a high retrieve speed (if casting for them from the boat) spooled with a good casting 30lb braid like Power Pro, Spider Wire or TuffLineXP. Don't even waste your time/money experimenting with the others. I use one of my bass rods for snoek, a Daiwa Sol 6'6 medium with a Shimano Calais 200dc 7.01:1 retrieve. This does seem a bit over the top, but when it comes to distance and accuracy on your cast with a light spoon - this is the ultimate combination.
If you are trolling you must be doing around 8knots (16kph), and once you hit them mark it on the gps, and keep doing this every time you get a bump. I would normally stop and cast to the leaders in the shoal and reel in at speed, don't pause if you see your lure being chased, keep reeling.
Here are some of my primary lures, start with a medium size like the silver/red head. If there are big snoek in the shoal go slightly bigger, if the bite seems to turn off for no apparant reason, switch to the baby little ones on a 12lb leader.
