I have fished a lot from the beach on Oahu and the Big Island, but same techniques will apply in Kauai. Whipping is probably the most popular method or Dunking. Do a you tube search for Braddahs shore fishing tips and techniques if your unfamiliar with whipping or dunking. They have some good how to videos and there are also others. As to where to fish, can't help there. Best tips for spots to fish have come from people I ask who are working in some local store, not necessarily a fishing store.

For example, the Boyz at Enterprise Rent a Car told me about some great locations when I showed up to pick up my car. Whipping and Dunking do not require much gear.

Good luck and Great Trip.

Mike