Doing this all the time at race venues as well as in the shop...
I have done them blind with no liners (SUUUCKS). I prefer liners. Cut the heads off the inner and run a liner - bam done. My favorite is a bright light and a j bend spoke - especially on rear brakes through the top tube. Reach in- hook the cable and pull it out.
I do not use any of the routing tools. They all seem nice but I just haven't really needed them. Adding anything to the cable would have created problems in a few situations.
It's a brake cable on an easy frame. Just get it done. You probably don't need anything but I say that knowing I have a whole bag of tricks and experience to throw at it. Just be patient and think of it as a learning experience. Then when done you will understand how stupid it is. Good only for looks and a make believe aero benefit that makes no difference to anyone really.