What I generally do is in smb.conf add a create mask like so:
Code:
[sharename]
comment = Shared Dir
path = /path/to/dir
read only = no
public = yes
write list = @smbusers
force group = smbusers
force create mode = 0664
force directory mode = 0775
Then add all of the users to be able to write to that directory to the smbusers group (you'll need to create the group):
Code:
usermod -G smbusers username
Set the directory setgid (chmod g+s /dirname is the easiest)
then chown the directory to root.smbusers (don't forget to also chown any existing files as well)