Permissions on auto-mounted usb vfat drives

[hansonry]

I want to set up my auto mounted usb external drive so that I can rwx the drive but my brother (who has an account on my system) can only r. I like the auto mount feature and my brother only remotely logs in and has no access to the physical drive. I have tried editing /etc/fstab and it kindof worked. It would do everything except for unmount :(

Any ideas would be very useful. I don't mind creating groups to get this working.

Thanks much!