fonts/etc_fonts/conf.avail/10-hinting-medium.conf

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>
<!--  Use Medium Hinting --> 
  <match target="font">
    <edit name="hintstyle" mode="assign"><const>hintmedium</const></edit>
  </match>
</fontconfig>