Worth reflecting that there is manual and there is manual. On a lot of newer rides, it's less straightforward to move trains by directly controlling brakes and kickers, you often operate at 'block level' rather than manually controlling individual items.
On older rides without PLCs or with more primitive PLCs/relays, you have to be more creative as it is more of a manual process overall. When I working an Arrow looper we had a procession of maintenance guys fail to restart the ride, with one train on the lift and another in the safeties, the head mechanic switched off the PLC, messed around with a compressor to get the train moving out of the brakes and manually switched on the lift motor to get the train off the lift.