What tackle to use
9 - 12 wt outfits, large arbour reels that hold at least 200m of backing of you're after big Spaniards. Use wire trace.
What flies to use
Deceivers; Flashy Profiles; Popper; Crease fly; Gurgler; Things; Clouser.
Spaniards are mainly caught offshore as they are pelagic - search areas around headlands and reef pinnacles. The strike is usually extremely hard and fast as is the first run. Hold on!
Around bait schools and when using burley, a sinking line would be best. If the fish are feeding towards the surface then you could get away with an intermediate line.