Those grills look pretty sweet.  We've used the foil method for anytime we already have a fire, and don't want to hassle with frying.  The main thing is not filleting.  Remove the fish head and guts, but keep within the skin.  A little butter or oil, spices, and even some lemon slices will make it awesome.

Another tip is that if you have a good cooking fire, you won't need the grill.  We'll typically put foil wrapped fish directly on the coals.