[jyavenard]

Assuming there are no differences with how the fonts are stored between the Kindle 2 International 2.2 and 2.3 (from the few reports out there, it's the case)

You'd do something like:
#First extract the package for the Kindle 2 International
./packager-0.6/kindle_update_tool.py e update_ufh_droid_install-k2i.bin

#Extract the content
tar zxvf update_ufh_droid_install-k2i.bin.tgz

This creates the following file:

$ tar zxvf update_ufh_droid_install-k2i.bin.tgz
x install-droid.sh.sig
x install-droid.sh
x droid.ttf.sig
x droid.ttf
x update_ufh_droid_install-k2i.dat

#Remove all the files you don't need anymore
rm *.sig *.dat *.tgz

#Recreate the package
#For Kindle 2:
./packager-0.6/kindle_update_tool.py m --k2 --sign --ex ufh_droid_install-k2 install-droid.sh droid.ttf

#For Kindle DX:
./packager-0.6/kindle_update_tool.py m --dx --sign --ex ufh_droid_install-dx install-droid.sh droid.ttf

That's about it ...