I have just recently had the fortune of getting into saltwater fly and it ahs taken me a while to get my first snapper but now that i have i thought i would share some knowledge on how i managed to do it. These tips and ideas can be used on other species and i don't declare to be an expert. this is just what has worked for me.
You can start with your fly gear and in fact i have had some great fun on a 6weight and kahawai but as a starting rod i would go for a an 8 or nine weight and move up to a 12wt when you start targeting the really big snapper and even kingfish. if you are going to use your trout gear just remember to clean it after each use with lemon juice.
You can use a any type of rod in the salt but when targeting bigger snapper and other slat fish the reel is the main player and this will be tested. i first used a really cheap trout reel but the drag was no good so the first fish i hooked just stripped line till i was in the backing then busted me off. The other thing to think about with reels is start up inertia. basically the smoother the start up of the reel the less likely you will get a bust off when you first hook a fish.
This is one of the most important factors because if the fish aren't there they just aren't there. There seems to be two main water types. One is reefs where they can cruise around and pick up crabs and shrimps and the other is where there is current as they can sit and pick off food coming at them like a conveyor belt. Snapper also love having cover close by so anywhere they can hide like kelp is also good. The other thing is larger snappers diet changes as they get older so to bait fish so anywhere there are large congregations of baitfish will have snapper. So the main things to look at are structure and food.
I have had good success with clousers in a size 6 which is quite small and the bigger the fly the bigger the fish but i would start small to get an idea of what works and then start sizing up.
Here are a couple of flies that have worked for me. Having lots of flash adds to the attraction as baitfish have plenty when you see them in the water. other good flies are the interceptors, deceivers etc. action is the major factor (hence the clousers) and depth.
When fishing reefs you can use a float line with a sink tip or an intermediate line as the water depth is pretty shallow. You can vary the weight of your flies with the dumbell eyes to get extra depth or even use a heavier sinking line.
If fishing from rock points into deeper water you may need to sue a sink tip or and inter with heavier flies with split shot of heavier dumbells. tying with marabou will require heavier weight to get down.
This takes a bit of experimentation to see what works for you but here is what has worked for me. Cast out and strip twice to get in contact with your flies. Stop and count down from 5 or 10 depending on the depth you may even need to count to 15. Keep an eye on the line for movement and strip strike if you see it suddenly move. Then strip 5 times of approx. 3 inches of line quite quickly then stop and count to 5 then strip 5 times again. and repeat. you will usually find that the fish will take just as you start to retrieve after the pause.
So far i have caught 8 fish with this method and will keep experimenting. Other retrieves may depend on the flies and the type of flies. EG for interceptors or crustaceans you may want to settle on the bottom and move very slowly.
Unlike the traditional trout strike the strike for sea fish is slightly different. as you will usually have your rod pointed at the water all you need to do is strip the line and raise the rod.
Always keep pressure on as fish can shake a fly out if you get too mush slack. Snapper will usually look for structure to hide and this is usually kelp so keep the pressure on and try putting your rod side on to the fish and change directions regularly to keep them off guard and tire them out more. If you get stuck in the kelp let your line go slack for a few minutes and then put the pressure on and try and walk it out. i have found this works.