[CentOS] Updating the DVD ISO howto?

I seem to remember this being addressed before, but I can't find the 
howto anywhere.

I've got a friend heading to another country with VERY limited 
bandwidth.  He'd like me to update the 4.4 DVD to include all of the 
updated RPMS from updated.

Where can I find the scripts to update the meta data on the RPMS and 
create a new bootable DVD?

Thanks!

Ben