Hi
Are you propagating POSIX permissions or ACL Permissions? if you're only propagating POSIX permissions it won't work and you'll soon end up back to only creator/owners of files and/or folders having read/write access and everyone else read only.
If you are propagating ACLs and you're having to do this regularly then there's something wrong elsewhere? It's a good idea not to share the volume but rather a folder within the volume. If ACL permissions are not propating properly or they are not sticking after propagation then un-share the share, rename the folder, create another folder named the same as it was before you renamed it and transfer the contents of the olf folder to the new onr. Re-share that new folder, add users or groups to the ACL Window, define appropriate permissions and re-propagate. This should now work without any further propagation.
If it's still not working I would start troubleshooting possible drive/directory issues. Use something like DiskWarrior or even Disk Utility. If the share(s) are on a non-boot volume then un-share the shares, do what you have to and re-share them again. Re-propagate afterwards. I can assure you this does work and works well but if there are underlying issues with either the Server Configuration (possible) or the drive/directory structure (more likeley) of the volume where the shares are stored you will see problems.
HTH?
Tony