Fishing into existing nailed-on plastic box

[Chamuit]

If you have ladder-blocking in the way and a usable hole, drill three holes in the top plate. One to look through, one for the flashlight, and one to drop your chain or rod through.

 

[tortuga]

I just fished romex into four 100-year old knob and tube boxes in my house without cutting into any drywall lathe and plaster (or wallpaper!) at all.

.../...

(And yes, my romex that's all inside the walls does not have proper clamp connectors to the old-as-hell boxes. Oops.)

When I had to do this, I drill/tapped a 10-32 ground screw to the box and it secured the cable nicely.