I just bought a new-ray helicopter diecast toy. I want to modify it a bit, and one of the plan is to make holes for the windows (square, around 5mm by 5mm). What I'm thinking is to use dremel to drill a small hole (around 2mm diameter) and then enlarge the hole using dremel metal grinder bit. However, I'm not sure how to start. Dremel bit catalogue has drill bit for metal, for soft metal. I am not sure what kind of metal the diecast is. The thickness of the diecast is around 1mm. I also checked dremel speed guide chart, but could not find the speed for drilling.
Is it ok to use these drill bits for that purpose? What speed should I use?