Threading cable

[RobinClay]

I have a pair of old wall sconces, each with two branches. Each branch carries a batten lamp holder, fed by a pair of separate rubber-insulated cotton-covered wires. Obviously, both have perished. When I try to draw out the old wire, it tends to just break.....

Should I pull them both together ? I had thought to extract just one wire, and then use the other to pull the new flex through, but if I pull out both, THEN how do I insert the new ?.

Any suggestions ?

 

[RobinClay]

AND... if a wire breaks and leaves some in the middle... as it probably will....any suggestions for getting the blockage out ?