I need to know how to easily and safely test used guitar cabs and speakers
to ensure they are functioning at their correct Ohm rating.

Please anyone know how or can direct me to online beginner level tutorial ?

Is it possible to just plug some inexpensive test meter device into the cab sockets
and get a quick reliable reading.

eg, if a 4x12 has sockets and switching for 4/8/16 Ohms
then I need to confirm that all selected settings are working correctly.

..same question also for testing the contacts on individual speakers ???

cheers...