I use "Permagrit" Sanding sticks. If you build or repair models, these sanding sticks are invaluable! They also work on EPP foam very well.
"the first choice of abrasive tool for
professionals and modellers worldwide
Perma-Grit design and manufacture Tungsten Carbide grit abrasive tools for the Performance Car, Boat and Aircraft market. Our tools are renowned for their longevity and ability to work modern composite materials – Carbon Fibre, Kevlar, Glass Fibre, Perspex, Plexiglas, Lexan, Acrylics, Plastics and Polystyrenes and more conventional materials – Woods, Ceramics, Stone, Marble, Glass and Metal. Designed and used by Hobby and Prototype Model builders and high performance Aircraft, Boat and Formula 1 Racing Car manufacturers around the world."