remember talking some time ago with some of my most respectable instructors about this case ,of electrical smoke-fire inflight.
This can be one of the deadliest things that can happen inflight,especially after the disapeareance of the engineers from the cockpit.
It's some amount of work to be done,under stress,and also the necessity to proceed asap to land.
Also the NNC can be sometimes quite long.
The conclusion that I have from my previous discussions is that in such a case (electrical smoke-fire ) the wisest choice would be to depower the plane (as lem says ,gen off) and do a rapid descent inbound landing.
If remains time you may try to sort things out via the NNC..
Time can be very precious,and sometimes it may be not enaugh if you do it by the book...happened more then once
Brgds
Alex