Looking for toner level OID for nagios snmp for Brother 9460
The real issue here is whether or not Brother has built support into the printer to report out actual toner levels via SNMP. Looking at vendor specific MIB's is a good way to get an idea of what kind of information is supported.
Looking up Brother's MIB's - http://www.oidview.com/mibs/2435/BROTHER-MIB.html - we can see that they seem to only report out low toner, which explains why, when you use the standard printer MIB, you're limited to that "-3" / "I'm not low" status.
It is possible that information on that website is inaccurate though; really I would recommend you try to get Brother's MIBs directly from them - http://welcome.solutions.brother.com/BSC/public_s/id/managedprint/en/mib.html?reg=us&c=us_ot&lang=en&redirect=on
This is not guaranteed to work, but does with a few printers - if it does it saves a lot of trial and error.
Install the full sw/driver package which installs a utility in the system tray that reports printer status.
Install wireshark and start looking at whats going through your nic.
We are only interested in looking at SMNP traffic to/from the IP address of your printer.
Have a look and see which OID the s/w uses then try and set this in nagios.