When running wiring inside a trailer chassis, I use MIG wire with a short (300mm) length of fluorescent brickies stringline. The string always sits at the bottom and is easily seen because of the colour, making it easy to pick up with a wire hook. The end of the MIG wire is threaded into the wire, approx. 40mm, have it protrude and make a right angled hook to sink back into the wire, a layer of plastic tape makes the wire come out of the hole easily, as it's tapered to a point, and prevents the MIG wire coming off.
Hope this helps someone.