Run a spherical burr around the inside of the hole to enlarge it and remove all of the edges that might catch and cut the sleeve and wires.
Step drill the holes at the bottom of the bars where both lines are going to come out and through the top yoke. Run the burr and make sure the wholes are big enough to run both cables. The bigger the hole, the easier stuff will go through. Remember, you read it first here.
Run enough MIG wire through both holes to guide the cable
Spray some WD40, vaseline, olive oil, lard, used engine oil, cod liver oil, gay gel, or whatever you've got handy into the holes to make the stuff slide in better.
Anyway, to cheer me up I always remember the sayings on a " Exile-hide-your-softail-coil-under-the-engine-kit-for-a-thousand-British-pounds-or-so" instruction leaflet:
"Now enjoy the clean look of your engine" Laaaaaaavelly...