# users: wilma, betty
# group: devs contains wilma and betty.
# directory: 'dir'

chgrp -R devs dir
find dir -type d -exec chmod 2770 {} +
find dir -type f -exec chmod 660 {} +
setfacl -d -R -m group:devs:rwx dir
setfacl    -R -m group:devs:rwx dir