Spray-on expanding foam insulation is very effective. The most common brand that I know of is Icynene. Plan on spending big bucks for it up front, but it is much better than conventional batt or blown insulation, so eventually you'll offset the savings in energy costs. It is not a DIY product.
EPS foamboard is not a good product for use in walls or attics. It can't be left exposed in the attic, and is best used where intended...Below grade or as an insulative sheathing material.