So mine work as follows:
You engage the reversers with throttles at idle (because that is the only throttle position you would do this with in real life).
You then need to advance the throttles just slightly to get the REV lights to indicate that the reversers are active (consider this a bug with the Honeycomb Bravo I guess).
You can further advance the throttles if you need more than idle reverse thrust and reduce them back to idle as necessary.
After disengaging the reversers, the throttles again need to be moved just slightly for the disengagment to actually occur (as indicated by the REV lights extinguishing).
Hope this is helpful and answers your question.