1) R2S sea rocks actually work
2) At least my mainline, up to twice it.
3) Mix it up till you get whacked.
4) Around the edges, the one with the fish on it.

pirates work really well, shout lightens, stays, twinchips, sacrifice leafs. Dhuies are fussy

60lb flouro leaders

i try to do as little as possible but still keeping the jig close to the botttom

i sound fish and drop right on them

i'm just getting into it,  but agree with the lightens and def SS hookers, sweetened with the fanky style rubber squid.  between 80 - 130 grams on 40lb fluro trace of 4 meters. (only because i've watched skippy being line shy at the surface when they spot the braid , and i suspect big dhueys aren't stupid)

...cheaper jigs can catch just as well as the more expensive ones. Jamie's sea rock suggestion is spot on. Shortish, fattish baitfish profiles as opposed to the more slender knife styles popular for sambos/ambos/skippy. The other key factor, as already said, try to drop straight onto the fish. Got four dhuies in Jurien that all hit the jig within 30 seconds of it reaching the bottom. That was mostly on flat patches of coral, with one notable lump in the mix.

I use 48 lb mainline (best to use proper jigging line, which is braid, but much thinner for its strength) and I tie a bimini and use either an albright or yucatan knot to join it to 60 lb Penn 10x. My leader is around 2-3 rod lengths. And if you're specifically after dhuis, use big assist hooks, and high quality ones...the ones from shout are really good, see honsu on that one.

1. Favourite jigs are Evergeen Caprice and Shout Stays. Favourite colour red and gold.  I try and use the smallest weighted jig as possible. Try to keep the jig directly below the boat.

2. I use PE3 and 60lb wind ons.

3. Try to mix it up a bit with technique. Most of the time I do one short jig followed by one long jig then allow the jig to drop back a bit and take up the slack line. Repeat this 5 times and drop the jig back down to the bottom. Go as slow as possible Dhuys are pretty lazy. Allowing the jig to drop a bit is the key. Gives the jig the fluttering action they are designed for.

4. Try and work the jig through any bait schools. Best results I had is when dhuys are feeding on a bait school. The jig should act like a small fish fleeing from the school. I find jigs work really well on large structures as well. Theres a couple of well know lumps down south that don't fish baits that well but run a jig over them and its a different story.

pretty much the same as above.
1. anywhere between 60-100gm depending on speed of the drift. Fluttering jigs worked well for me

2. usually 60lb leader with 20-30lb braid for my mainline

3. lift, lift, lift then give it heaps of free line so it flutters back down. Sometimes you need to let more line out so it hits the bottom again

4. Sound around for the fish, then position the boat just upwind/current and try to drop onto them. Keep jigging as you drift over then go back and do it again

Mate in my personal experience if theres dhuies about they will just about eat anything you put infront of them unless theres a northerly tide or something else shutting them down.Favourite jigs of mine are the shout lightens and zests.Keep trying different techniques until something works.Use your sounder to find the fish and drop on top of them 50% of time i get hit on the first drop.