Cutting Stereo Fascia

I recently installed a new head unit, but while it is a single din unit it is just a couple mm too big to sit right & I need to trim my fascia so that it will fit better. What is the best way to trim it ? I have tried search but couldn't find anything on the best method.

 

A dremel, or good old block and sandpaper. Maybe a file.

 

100 grit paper glued to wooden block. Start sanding. Anything else will rip the material off too fast