I use a 1/0 hook on a short 14 pnd flouro leader...
Raw and cooked both work equally as well for me, but I definitely prefer natural for steelhead and rarely dye them or do anything else.
At times I will add a bit of orange wool in the bait loops. Seems to give a spotting effect and also will hold the prawn on longer. I just add the prawn directly onto the hook and slide it up to the wool in the bait loop. Definitely a durable bait. I should mention here that I never or very rarely use a full prawn, mostly just small chuncks like you would use to tip a jig with. I have died full prawns pink before and threaded them on with a needle above the hook. Kind of like a 3" pink worm with scent, that spins like crazy in the water. Careful reeling those guys in... had lots of larger bull trout take them top water, and even a steelhead once.
And I'll echo what Big Fisher says. Later in the season change is important. I was sight fishing this past weekend ans tried running bait, worms, corkies, wool ties, pretty much everything. Only got 1 fish on bait, 2 on worms and then 7 on spoons - and all these fish were behind people. Pays to show them something they haven't seen yet that day.
Cheers,
Dan