tailoring soft plastic types/colours?

I've started to doubt my collection and use of soft plastics lately. While a 5 inch gulp nuclear chicken will pick up flathead more or less consitently and often more reliably then dead or even live bait when flicked across the sand flats, i've found that my soft plastics are useless for just about everything else.
I started today flicking a few different styles and colours for mangrove jacks and got not a nibble, swapped to pilchards and got hammered by the buggers both big and small, i've noticed the same for snapper, macs, bream and just about every target species apart from the nobel flat head.

My question is weather each fish requires a specific style and action, and why does a lump of pilchard or inexpertly rigged livey do so much better.
Can someone shed some light on the best way to fish for bream, snapper and jacks using soft plastics, what colour and style to be using and how to work them?
i love the idea of fishing soft plastics as they are cheap, durable and easy to store and don't get you're hands all nasty for the sake of a quick flick after work, but i really do need to know how to get the damn things to work for my target species.

Different areas, different times of the day, different times of the year and different tide direction can all affect what your target fish is eating.
Currently almost anything that looks prawnish is a very safe bet. Head into March and flickbaits and paddletails will be more productive.
Run out tides have been producing more entertainment the past month for me.

If you are after bream the tip is keep it light, no heavier than 1/8 oz or less, I catch very very few bream on plastics now that I target flathead with 1/4 oz jig heads..

The most versatile plastic I have found is the squidgy wriggler 80mm in bloodworm - As much as it pains me to line Mr Starling's pockets. The species list I have caught with this is the longest by far of any of the virtual tackle shop I have managed to assemble over the years. In recent times I have also become a convert to using S-Factor as well - it certainly doesn't seem to put the fish off. As mentioned, fishing with the lightest possible jig head and fishing the lures SLOW seems to be the trick. Pauses between hops of 20 - 30 seconds can quite often result in the lure getting absolutely creamed as soon as it moves - if it doesn't get picked up off the bottom. The downside to these is they are ridiculously soft and the toadies love them so I also use the Z-Mann curly tails in 4 inch a bit as well. If we are specifically targeting snapper in the bay we tend to use 100 or 120mm and 5 inch Z-Manns

The ZMan Streakz Curly TailZ in 3.75" in Motor Oil colour will walk all over any other lure for flathead. Couple of other similar colours in that range are hot too. The same lure and colour will account for snapper in the Bay, as well as jacks in the canals and creeks.

With a single tail in that colour I have seen a mate of mine pull 30-49 flathead off a bank in a session.

Thanks for the advice guys, paid my money and took my chances on some prawn shaped softies with a bit of scent added. Seemed to go ok hopped down the side of a local creek with long pauses, 2 undersized jacks and one just leave in the space of two hours. It actually did really well compared to the bait, got many more hits on the bait but lots of cat-fish/small bream.
I's be interested to try some of the other recommendation at the weekend for fathead if i can't sneak offshore.