union sync files/dir to USB Flash Disk

Within gconf-editor, I used the "Find" tool to search for "vfat" (searching also in all key names and key values).

This returned the key "/system/storage/default_options/vfat"

I deleted the umask key, then added the 2 keys you suggested as follows:
dmask=022
fmask=133

Now all directories/folders on my vfat USB flash drives and USB external hard drives are presented with the permissions:

drwxr-xr-x

...and all files on my vfat USB flash drives and USB external hard drives are presented with the permissions:

-rw-r--r--