Here are the tools I used for this.

Top is a small file. Got it from Harbor Freight. But it is for big work.
The next 4 files are mini files from a discontinued Xacto set. If you ever see this set, buy it. Hopefully they will bring it back one day.
File #2 is a triangular file for the corners.
File 4 is a flat file for much of the work.
File 3 is a half moon file (flat on one side and curved on the other. It is a bit sharper on the edges than the plain flat file.
The square file at bottom is for rough work in the corners and the narrow edges.
Lastly, there is a #11 Xacto knife.