I was having some problems sanding some stuff.. and my normal files and sandpaper wouldn't reach the smal crevises.. so after asking some help and info at the amazing roup of proptarts (https://www.facebook.com/groups/theproptarts), i decided to desing my own sanding stick.
Its cheap, small and quick to print.

INFO: If you want a smaller or wider stick you just need to change X(or Y) axis and you are done =D

Extras you'll need:
-Sandpaper
-Glue or double sided tape