bulk permission change

I have recently taken over a tech post at a school and the previous techy had set up the file permissions defaults to not include admin (not even read).
I need to search all the users for specific files, but at the moment I'm having to set the permissions a folder at a time, there's a few hundered users so this is not going to be an option for all folders.

Is there any way of just adding a permission to all folders/subfolders while still keeping the current permissions?

I'm running NT4.
Cheers

ChannonP