did you try enabling anti-aliasing in kde control center? When you specify that some font sizes are to be excluded from aa-ing, it should create a .fonts.conf in your home directory. BTW, it's a hidden file as the leading . indicates.
I do NOT recomment editing /etc/fonts/fonts.conf
If nothing else, you can create a .fonts.conf in your home directory. After logging in again, the settings will take effect. Mine looks like this: It is set to anti-alias fonts smaller than 8pts and larger than 16pts, and leave the rest normal - you can change the numbers to your liking. For very small and very large things, anti-aliasing is good.
<match target="font" >
<test compare="more" name="size" qual="any" >
<test compare="less" name="size" qual="any" >
<edit mode="assign" name="antialias" >