You could always modify your smb.conf file by hand. Here is an example read-only share:
[share_name]
comment = Share_comment
security = share
public = yes
force user = nobody
force group = nogroup
inherit acls = No
path = /path/to/share
read only = Yes
To give write access, just set read only to No. I haven't tested it with eBox, but I had a server that used a similar share.
I assume a similar thing could be done with printers by modifying the [printers] or [print$] sections of smb.conf, but I don't know for sure.
Good luck!