When romex is run across rafters in an open unfinished attic it is my position that a raceway of some kind 1x3 s or even 2x4 s should first be attached across the affected rafters perhaps 3 to 4 above the joists then the wiring be stapled to the raceway.
Running wires without attic.
Attach the wire or cable to a fish tape or coat hanger using electrical tape and feed it into the hole until it reaches the opening at the other end.
Watch the entire process step by step.
On a single story home or the the upper floor of a multiple story home this means accessing your attic to run wire.
The actual install of recessed lights here https youtu be 5yc8aqnvqqg the long bit is actually used.
You ll need two wires one white and one black for one circuit or more if you intend to wire a three way switch from the house or add more than one circuit.
If you re working from the attic you can drop a weighted string down wall cavity then attach the wire to the string and pull it through.
But if you have knob and tube running in an attic or exterior wall the space can not be insulated until the wiring is replaced.
Totally hidden existing knob and tube wiring meets code and we have left it in place inside some interior walls.