I don't know about a dash but I've had really good luck drilling holes by clamping your piece to be drilled between two pieces of wood. If you sandwich the dash really well it will stop the bits from walking and leave you with a clean hole. Have had best results using a drill press with the wood sandwich clamped to the surface of the drill press. *DISCLAIMER* I've only tried this on materials like formica, rare or expensive woods, and a steel Jeep dash. The Jeep dash was drilled to put in a factory clock and tach (old CJ7)and it worked really well.
Chad