I would try one of the tracers. You need one with pretty decent power - I would think. I have not used one. Because of the conduit, you would need to get to the fixtures/devices to tell or get to actual wires. Hook the tracer to the incoming lines. If 3 phase, you probably need to short the 3 phases together and hook up the tracer phase to ground.

If not obvious, you shut all the breakers off and turn them on one by one till the tracer beeps. Alternatively, you can short out each fixture/device and measure resistance on the incoming lines, but I would try a tracer.

It is very doable but will take some time.

Good luck!