Help with finding/choosing a remote flash trigger

[RWAcarol]

Hi.

I have an A7Rii and am struggling to understand what remote flash trigger to buy.

Currently I have a Neewer TT-560 flash and a Neewer VC-16 trigger - however I want to upgrade to a second off-camera flash/strobe and I cannot get a second receiver as the VC-16 is no longer produced, so need a new trigger with at least 2 receivers to work my existing flash and whatever new one I buy.

Am I correct in thinking that only the transmitter needs to be Sony compatible - and that any receivers it comes with will work with any flash/strobe etc? I assume you just hook the receiver to the flash unit with the cable if it doesn't have a hot shoe or is not compatible with it?

Does anyone have any recommendations for a trigger + 2 receiver set-up?

Sorry if this question is very basic but I am a newby to using off-camera flash.

Thanks in advance.