Can't help you with the automounter, but the following steps should help you access the usb drive contents until you get that figured out.
# cd /mnt && mkdir usb-drive
# chmod o+rw usb-drive
# mount -t vfat /dev/sdb /mnt/usb-drive
Then your regular users should have access to the contents under /mnt/usb-drive. When you're done with it, don't just pull it out of the PC. Use
# umount /mnt/usb-drive