Location, location, location
While I've been a fly fisherman for a long time, I've never consciously fished for kings in the salt. I have, however, towed a lot of cut plugs for same.
My thought is that if you really want to hit kings in the salt, you need to be in the right location--- and here I'm talking more of a type of area than Neah Bay or Sekiu. From my two decades of king chasing, I know of three such spots that hold kings that are actively feeding in shallow enough waters to be in fly range. Unfortunately, all three such spots are in the eastern Strait and now closed for kings. But, pardon my bass-fishing background here, the key is the kind of structure the fish hold on. Two of the spots that hold these shallow kings are sandspits with enough current passing by to sweep baitfish to waiting predators. Another is an area where kings will cruise by on the surface even during the middle of the day. This last place is the only spot I've ever seen that happen, and I couldn't tell you why they do it there, but they do...
Another possibility is to do the pre-dawn patrol when kings will be on or very near the surface. This might be a trolling show rather than a casting show because the kings I've caught during the dark hours were always taken on a fast, silver troll. They always hit close to the boat on the surface.
With luck, I may be home enough this summer to give 'em a whack, but I'd have to hit a run right on the money. We'll see.